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OpenCloudOS-Kernel/kernel/trace/ring_buffer.c

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tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/*
* Generic ring buffer
*
* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
*/
#include <linux/ring_buffer.h>
tracing: implement trace_clock_*() APIs Impact: implement new tracing timestamp APIs Add three trace clock variants, with differing scalability/precision tradeoffs: - local: CPU-local trace clock - medium: scalable global clock with some jitter - global: globally monotonic, serialized clock Make the ring-buffer use the local trace clock internally. Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-27 01:47:11 +08:00
#include <linux/trace_clock.h>
ring-buffer: add NMI protection for spinlocks Impact: prevent deadlock in NMI The ring buffers are not yet totally lockless with writing to the buffer. When a writer crosses a page, it grabs a per cpu spinlock to protect against a reader. The spinlocks taken by a writer are not to protect against other writers, since a writer can only write to its own per cpu buffer. The spinlocks protect against readers that can touch any cpu buffer. The writers are made to be reentrant with the spinlocks disabling interrupts. The problem arises when an NMI writes to the buffer, and that write crosses a page boundary. If it grabs a spinlock, it can be racing with another writer (since disabling interrupts does not protect against NMIs) or with a reader on the same CPU. Luckily, most of the users are not reentrant and protects against this issue. But if a user of the ring buffer becomes reentrant (which is what the ring buffers do allow), if the NMI also writes to the ring buffer then we risk the chance of a deadlock. This patch moves the ftrace_nmi_enter called by nmi_enter() to the ring buffer code. It replaces the current ftrace_nmi_enter that is used by arch specific code to arch_ftrace_nmi_enter and updates the Kconfig to handle it. When an NMI is called, it will set a per cpu variable in the ring buffer code and will clear it when the NMI exits. If a write to the ring buffer crosses page boundaries inside an NMI, a trylock is used on the spin lock instead. If the spinlock fails to be acquired, then the entry is discarded. This bug appeared in the ftrace work in the RT tree, where event tracing is reentrant. This workaround solved the deadlocks that appeared there. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-06 07:43:07 +08:00
#include <linux/ftrace_irq.h>
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
ring-buffer: use generic version of in_nmi Impact: clean up Now that a generic in_nmi is available, this patch removes the special code in the ring_buffer and implements the in_nmi generic version instead. With this change, I was also able to rename the "arch_ftrace_nmi_enter" back to "ftrace_nmi_enter" and remove the code from the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-06 14:45:16 +08:00
#include <linux/hardirq.h>
trace: annotate bitfields in struct ring_buffer_event This gets rid of a heap of false-positive warnings from the tracer code due to the use of bitfields. [rebased for mainline inclusion] Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
2009-02-28 15:29:44 +08:00
#include <linux/kmemcheck.h>
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/mutex.h>
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 16:04:11 +08:00
#include <linux/slab.h>
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/list.h>
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
#include <linux/cpu.h>
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
#include <linux/fs.h>
local_t: Move local.h include to ringbuffer.c and ring_buffer_benchmark.c ringbuffer*.c are the last users of local.h. Remove the include from modules.h and add it to ringbuffer files. Signed-off-by: Christoph Lameter <cl@linux-foundation.org> Signed-off-by: Tejun Heo <tj@kernel.org>
2010-01-05 14:34:50 +08:00
#include <asm/local.h>
ftrace: insert in the ftrace_preempt_disable()/enable() functions Impact: use new, consolidated APIs in ftrace plugins This patch replaces the schedule safe preempt disable code with the ftrace_preempt_disable() and ftrace_preempt_enable() safe functions. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-04 12:15:56 +08:00
#include "trace.h"
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
/*
* The ring buffer header is special. We must manually up keep it.
*/
int ring_buffer_print_entry_header(struct trace_seq *s)
{
int ret;
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
ret = trace_seq_printf(s, "# compressed entry header\n");
ret = trace_seq_printf(s, "\ttype_len : 5 bits\n");
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
ret = trace_seq_printf(s, "\ttime_delta : 27 bits\n");
ret = trace_seq_printf(s, "\tarray : 32 bits\n");
ret = trace_seq_printf(s, "\n");
ret = trace_seq_printf(s, "\tpadding : type == %d\n",
RINGBUF_TYPE_PADDING);
ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
RINGBUF_TYPE_TIME_EXTEND);
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
ret = trace_seq_printf(s, "\tdata max type_len == %d\n",
RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
return ret;
}
ring-buffer: document reader page design In a private email conversation I explained how the ring buffer page worked by using silly ASCII art. Ingo suggested that I add that to the comments of the code. Here it is. Requested-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 10:24:17 +08:00
/*
* The ring buffer is made up of a list of pages. A separate list of pages is
* allocated for each CPU. A writer may only write to a buffer that is
* associated with the CPU it is currently executing on. A reader may read
* from any per cpu buffer.
*
* The reader is special. For each per cpu buffer, the reader has its own
* reader page. When a reader has read the entire reader page, this reader
* page is swapped with another page in the ring buffer.
*
* Now, as long as the writer is off the reader page, the reader can do what
* ever it wants with that page. The writer will never write to that page
* again (as long as it is out of the ring buffer).
*
* Here's some silly ASCII art.
*
* +------+
* |reader| RING BUFFER
* |page |
* +------+ +---+ +---+ +---+
* | |-->| |-->| |
* +---+ +---+ +---+
* ^ |
* | |
* +---------------+
*
*
* +------+
* |reader| RING BUFFER
* |page |------------------v
* +------+ +---+ +---+ +---+
* | |-->| |-->| |
* +---+ +---+ +---+
* ^ |
* | |
* +---------------+
*
*
* +------+
* |reader| RING BUFFER
* |page |------------------v
* +------+ +---+ +---+ +---+
* ^ | |-->| |-->| |
* | +---+ +---+ +---+
* | |
* | |
* +------------------------------+
*
*
* +------+
* |buffer| RING BUFFER
* |page |------------------v
* +------+ +---+ +---+ +---+
* ^ | | | |-->| |
* | New +---+ +---+ +---+
* | Reader------^ |
* | page |
* +------------------------------+
*
*
* After we make this swap, the reader can hand this page off to the splice
* code and be done with it. It can even allocate a new page if it needs to
* and swap that into the ring buffer.
*
* We will be using cmpxchg soon to make all this lockless.
*
*/
ring-buffer: add tracing_off_permanent Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-22 01:41:55 +08:00
/*
* A fast way to enable or disable all ring buffers is to
* call tracing_on or tracing_off. Turning off the ring buffers
* prevents all ring buffers from being recorded to.
* Turning this switch on, makes it OK to write to the
* ring buffer, if the ring buffer is enabled itself.
*
* There's three layers that must be on in order to write
* to the ring buffer.
*
* 1) This global flag must be set.
* 2) The ring buffer must be enabled for recording.
* 3) The per cpu buffer must be enabled for recording.
*
* In case of an anomaly, this global flag has a bit set that
* will permantly disable all ring buffers.
*/
/*
* Global flag to disable all recording to ring buffers
* This has two bits: ON, DISABLED
*
* ON DISABLED
* ---- ----------
* 0 0 : ring buffers are off
* 1 0 : ring buffers are on
* X 1 : ring buffers are permanently disabled
*/
enum {
RB_BUFFERS_ON_BIT = 0,
RB_BUFFERS_DISABLED_BIT = 1,
};
enum {
RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
};
tracing: fix sparse warnings: fix (un-)signedness Fix these sparse warnings: kernel/trace/ring_buffer.c:70:37: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:84:39: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:96:43: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2475:13: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2475:13: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2478:42: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2478:42: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2500:40: warning: incorrect type in argument 3 (different signedness) kernel/trace/ring_buffer.c:2505:44: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2507:46: warning: incorrect type in argument 2 (different signedness) kernel/trace/trace.c:2130:40: warning: incorrect type in argument 3 (different signedness) kernel/trace/trace.c:2280:40: warning: incorrect type in argument 3 (different signedness) Signed-off-by: Hannes Eder <hannes@hanneseder.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-11 02:44:34 +08:00
static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
/**
* tracing_on - enable all tracing buffers
*
* This function enables all tracing buffers that may have been
* disabled with tracing_off.
*/
void tracing_on(void)
{
ring-buffer: add tracing_off_permanent Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-22 01:41:55 +08:00
set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(tracing_on);
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
/**
* tracing_off - turn off all tracing buffers
*
* This function stops all tracing buffers from recording data.
* It does not disable any overhead the tracers themselves may
* be causing. This function simply causes all recording to
* the ring buffers to fail.
*/
void tracing_off(void)
{
ring-buffer: add tracing_off_permanent Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-22 01:41:55 +08:00
clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(tracing_off);
ring-buffer: add tracing_off_permanent Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-22 01:41:55 +08:00
/**
* tracing_off_permanent - permanently disable ring buffers
*
* This function, once called, will disable all ring buffers
tracing: fix typos in comments Impact: clean up. Fix typos in the comments. Signed-off-by: Wenji Huang <wenji.huang@oracle.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-10 14:03:18 +08:00
* permanently.
ring-buffer: add tracing_off_permanent Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-22 01:41:55 +08:00
*/
void tracing_off_permanent(void)
{
set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
}
ring-buffer: add tracing_is_on to test if ring buffer is enabled This patch adds the tracing_is_on() interface to tell if the ring buffer is turned on or not. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-15 08:17:02 +08:00
/**
* tracing_is_on - show state of ring buffers enabled
*/
int tracing_is_on(void)
{
return ring_buffer_flags == RB_BUFFERS_ON;
}
EXPORT_SYMBOL_GPL(tracing_is_on);
ring-buffer: replace sizeof of event header with offsetof Impact: fix to possible alignment problems on some archs. Some arch compilers include an NULL char array in the sizeof field. Since the ring_buffer_event type includes one of these, it is better to use the "offsetof" instead, to avoid strange bugs on these archs. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 02:53:07 +08:00
#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
kernel/trace/ring_buffer.c: use DIV_ROUND_UP Instead of open-coding it. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
#define RB_ALIGNMENT 4U
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
ring-buffer: prevent adding write in discarded area This a very tight race where an interrupt could come in and not have enough data to put into the end of a buffer page, and that it would fail to write and need to go to the next page. But if this happened when another writer was about to reserver their data, and that writer has smaller data to reserve, then it could succeed even though the interrupt moved the tail page. To pervent that, if we fail to store data, and by subtracting the amount we reserved we still have room for smaller data, we need to fill that space with "discarded" data. [ Impact: prevent race were buffer data may be lost ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-11 23:12:00 +08:00
#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
ring-buffer: Do 8 byte alignment for 64 bit that can not handle 4 byte align The ring buffer uses 4 byte alignment while recording events into the buffer, even on 64bit machines. This saves space when there are lots of events being recorded at 4 byte boundaries. The ring buffer has a zero copy method to write into the buffer, with the reserving of space and then committing it. This may cause problems when writing an 8 byte word into a 4 byte alignment (not 8). For x86 and PPC this is not an issue, but on some architectures this would cause an out-of-alignment exception. This patch uses CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to determine if it is OK to use 4 byte alignments on 64 bit machines. If it is not, it forces the ring buffer event header to be 8 bytes and not 4, and will align the length of the data to be 8 byte aligned. This keeps the data payload at 8 byte alignments and will allow these machines to run without issue. The trick to this is that the header can be either 4 bytes or 8 bytes depending on the length of the data payload. The 4 byte header has a length field that supports up to 112 bytes. If the length of the data is more than 112, the length field is set to zero, and the actual length is stored in the next 4 bytes after the header. When CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is not set, the code forces zero in the 4 byte header forcing the length to be stored in the 4 byte array, even with a small data load. It also forces the length of the data load to be 8 byte aligned. The combination of these two guarantee that the data is always at 8 byte alignment. Tested-by: Frederic Weisbecker <fweisbec@gmail.com> (on sparc64) Reported-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-19 05:54:19 +08:00
#if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
# define RB_FORCE_8BYTE_ALIGNMENT 0
# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
#else
# define RB_FORCE_8BYTE_ALIGNMENT 1
# define RB_ARCH_ALIGNMENT 8U
#endif
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
enum {
RB_LEN_TIME_EXTEND = 8,
RB_LEN_TIME_STAMP = 16,
};
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
static inline int rb_null_event(struct ring_buffer_event *event)
{
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
}
static void rb_event_set_padding(struct ring_buffer_event *event)
{
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
/* padding has a NULL time_delta */
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
event->type_len = RINGBUF_TYPE_PADDING;
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
event->time_delta = 0;
}
kernel/trace/ring_buffer.c: reduce inlining text data bss dec hex filename before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o Also: free_page(0) is legal. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
static unsigned
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
rb_event_data_length(struct ring_buffer_event *event)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
unsigned length;
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
if (event->type_len)
length = event->type_len * RB_ALIGNMENT;
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
else
length = event->array[0];
return length + RB_EVNT_HDR_SIZE;
}
/* inline for ring buffer fast paths */
static unsigned
rb_event_length(struct ring_buffer_event *event)
{
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
switch (event->type_len) {
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
case RINGBUF_TYPE_PADDING:
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
if (rb_null_event(event))
/* undefined */
return -1;
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
return event->array[0] + RB_EVNT_HDR_SIZE;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
case RINGBUF_TYPE_TIME_EXTEND:
return RB_LEN_TIME_EXTEND;
case RINGBUF_TYPE_TIME_STAMP:
return RB_LEN_TIME_STAMP;
case RINGBUF_TYPE_DATA:
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
return rb_event_data_length(event);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
default:
BUG();
}
/* not hit */
return 0;
}
/**
* ring_buffer_event_length - return the length of the event
* @event: the event to get the length of
*/
unsigned ring_buffer_event_length(struct ring_buffer_event *event)
{
ring_buffer: fix ring_buffer_event_length() Function ring_buffer_event_length() provides an interface to detect the length of data stored in an entry. However, the length contains offsets depending on the internal usage. This makes it unusable. This patch fixes this and now ring_buffer_event_length() returns the alligned length that has been used in ring_buffer_lock_reserve(). Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Robert Richter <robert.richter@amd.com>
2009-01-07 22:32:11 +08:00
unsigned length = rb_event_length(event);
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
ring_buffer: fix ring_buffer_event_length() Function ring_buffer_event_length() provides an interface to detect the length of data stored in an entry. However, the length contains offsets depending on the internal usage. This makes it unusable. This patch fixes this and now ring_buffer_event_length() returns the alligned length that has been used in ring_buffer_lock_reserve(). Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Robert Richter <robert.richter@amd.com>
2009-01-07 22:32:11 +08:00
return length;
length -= RB_EVNT_HDR_SIZE;
if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
length -= sizeof(event->array[0]);
return length;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_event_length);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/* inline for ring buffer fast paths */
kernel/trace/ring_buffer.c: reduce inlining text data bss dec hex filename before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o Also: free_page(0) is legal. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
static void *
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
rb_event_data(struct ring_buffer_event *event)
{
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/* If length is in len field, then array[0] has the data */
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
if (event->type_len)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return (void *)&event->array[0];
/* Otherwise length is in array[0] and array[1] has the data */
return (void *)&event->array[1];
}
/**
* ring_buffer_event_data - return the data of the event
* @event: the event to get the data from
*/
void *ring_buffer_event_data(struct ring_buffer_event *event)
{
return rb_event_data(event);
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_event_data);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
#define for_each_buffer_cpu(buffer, cpu) \
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
for_each_cpu(cpu, buffer->cpumask)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
#define TS_SHIFT 27
#define TS_MASK ((1ULL << TS_SHIFT) - 1)
#define TS_DELTA_TEST (~TS_MASK)
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
/* Flag when events were overwritten */
#define RB_MISSED_EVENTS (1 << 31)
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
/* Missed count stored at end */
#define RB_MISSED_STORED (1 << 30)
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
struct buffer_data_page {
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
u64 time_stamp; /* page time stamp */
tracing: fix typos in comments Impact: clean up. Fix typos in the comments. Signed-off-by: Wenji Huang <wenji.huang@oracle.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-10 14:03:18 +08:00
local_t commit; /* write committed index */
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
unsigned char data[]; /* data of buffer page */
};
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/*
* Note, the buffer_page list must be first. The buffer pages
* are allocated in cache lines, which means that each buffer
* page will be at the beginning of a cache line, and thus
* the least significant bits will be zero. We use this to
* add flags in the list struct pointers, to make the ring buffer
* lockless.
*/
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
struct buffer_page {
ring-buffer: record page entries in buffer page descriptor Currently, when the ring buffer writer overflows the buffer and must write over non consumed data, we increment the overrun counter by reading the entries on the page we are about to overwrite. This reads the entries one by one. This is not very effecient. This patch adds another entry counter into each buffer page descriptor that keeps track of the number of entries on the page. Now on overwrite, the overrun counter simply needs to add the number of entries that is on the page it is about to overwrite. [ Impact: speed up of ring buffer in overwrite mode ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-02 06:44:45 +08:00
struct list_head list; /* list of buffer pages */
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
local_t write; /* index for next write */
ring-buffer: move page indexes into page headers Remove the global head and tail indexes and move them into the page header. Each page will now keep track of where the last write and read was made. We also rename the head and tail to read and write for better clarification. This patch is needed for future enhancements to move the ring buffer to a lockless solution. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:58 +08:00
unsigned read; /* index for next read */
ring-buffer: record page entries in buffer page descriptor Currently, when the ring buffer writer overflows the buffer and must write over non consumed data, we increment the overrun counter by reading the entries on the page we are about to overwrite. This reads the entries one by one. This is not very effecient. This patch adds another entry counter into each buffer page descriptor that keeps track of the number of entries on the page. Now on overwrite, the overrun counter simply needs to add the number of entries that is on the page it is about to overwrite. [ Impact: speed up of ring buffer in overwrite mode ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-02 06:44:45 +08:00
local_t entries; /* entries on this page */
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
unsigned long real_end; /* real end of data */
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
struct buffer_data_page *page; /* Actual data page */
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
};
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/*
* The buffer page counters, write and entries, must be reset
* atomically when crossing page boundaries. To synchronize this
* update, two counters are inserted into the number. One is
* the actual counter for the write position or count on the page.
*
* The other is a counter of updaters. Before an update happens
* the update partition of the counter is incremented. This will
* allow the updater to update the counter atomically.
*
* The counter is 20 bits, and the state data is 12.
*/
#define RB_WRITE_MASK 0xfffff
#define RB_WRITE_INTCNT (1 << 20)
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
static void rb_init_page(struct buffer_data_page *bpage)
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
{
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
local_set(&bpage->commit, 0);
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
}
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
/**
* ring_buffer_page_len - the size of data on the page.
* @page: The page to read
*
* Returns the amount of data on the page, including buffer page header.
*/
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
size_t ring_buffer_page_len(void *page)
{
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
return local_read(&((struct buffer_data_page *)page)->commit)
+ BUF_PAGE_HDR_SIZE;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
}
ring_buffer: reset buffer page when freeing Mathieu Desnoyers pointed out that the freeing of the page frame needs to be reset otherwise we might trigger BUG_ON in the page free code. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:40 +08:00
/*
* Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
* this issue out.
*/
kernel/trace/ring_buffer.c: reduce inlining text data bss dec hex filename before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o Also: free_page(0) is legal. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
static void free_buffer_page(struct buffer_page *bpage)
ring_buffer: reset buffer page when freeing Mathieu Desnoyers pointed out that the freeing of the page frame needs to be reset otherwise we might trigger BUG_ON in the page free code. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:40 +08:00
{
kernel/trace/ring_buffer.c: reduce inlining text data bss dec hex filename before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o Also: free_page(0) is legal. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
free_page((unsigned long)bpage->page);
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
kfree(bpage);
ring_buffer: reset buffer page when freeing Mathieu Desnoyers pointed out that the freeing of the page frame needs to be reset otherwise we might trigger BUG_ON in the page free code. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:40 +08:00
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/*
* We need to fit the time_stamp delta into 27 bits.
*/
static inline int test_time_stamp(u64 delta)
{
if (delta & TS_DELTA_TEST)
return 1;
return 0;
}
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: move calculation of event length The event length is calculated and passed in to rb_reserve_next_event in two different locations. Having rb_reserve_next_event do the calculations directly makes only one location to do the change and causes the calculation to be inlined by gcc. Before: text data bss dec hex filename 16538 24 12 16574 40be kernel/trace/ring_buffer.o After: text data bss dec hex filename 16490 24 12 16526 408e kernel/trace/ring_buffer.o [ Impact: smaller more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 02:42:53 +08:00
/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
ring-buffer: discard timestamps that are at the start of the buffer Every buffer page in the ring buffer includes its own time stamp. When an event is recorded to the ring buffer with a delta time greater than what can be held in the event header, a time stamp event is created. If the the create timestamp falls over to the next buffer page, it is redundant because the buffer page holds a full time stamp. This patch will try to discard the time stamp when it falls to the start of the next page. This change also fixes a issues with disarding events. If most events are discarded, timestamps will start to creep into the ring buffer. If we do not discard the timestamps then they can fill up the ring buffer over time and waste space. This change will keep time stamps from filling up over another page. If something is recorded in the buffer page, and the rest is filtered, then the time stamps can only fill up to the end of the page. [ Impact: prevent time stamps from filling ring buffer ] Reported-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 21:30:10 +08:00
/* Max number of timestamps that can fit on a page */
ring-buffer: Fix typo of time extends per page Time stamps for the ring buffer are created by the difference between two events. Each page of the ring buffer holds a full 64 bit timestamp. Each event has a 27 bit delta stamp from the last event. The unit of time is nanoseconds, so 27 bits can hold ~134 milliseconds. If two events happen more than 134 milliseconds apart, a time extend is inserted to add more bits for the delta. The time extend has 59 bits, which is good for ~18 years. Currently the time extend is committed separately from the event. If an event is discarded before it is committed, due to filtering, the time extend still exists. If all events are being filtered, then after ~134 milliseconds a new time extend will be added to the buffer. This can only happen till the end of the page. Since each page holds a full timestamp, there is no reason to add a time extend to the beginning of a page. Time extends can only fill a page that has actual data at the beginning, so there is no fear that time extends will fill more than a page without any data. When reading an event, a loop is made to skip over time extends since they are only used to maintain the time stamp and are never given to the caller. As a paranoid check to prevent the loop running forever, with the knowledge that time extends may only fill a page, a check is made that tests the iteration of the loop, and if the iteration is more than the number of time extends that can fit in a page a warning is printed and the ring buffer is disabled (all of ftrace is also disabled with it). There is another event type that is called a TIMESTAMP which can hold 64 bits of data in the theoretical case that two events happen 18 years apart. This code has not been implemented, but the name of this event exists, as well as the structure for it. The size of a TIMESTAMP is 16 bytes, where as a time extend is only 8 bytes. The macro used to calculate how many time extends can fit on a page used the TIMESTAMP size instead of the time extend size cutting the amount in half. The following test case can easily trigger the warning since we only need to have half the page filled with time extends to trigger the warning: # cd /sys/kernel/debug/tracing/ # echo function > current_tracer # echo 'common_pid < 0' > events/ftrace/function/filter # echo > trace # echo 1 > trace_marker # sleep 120 # cat trace Enabling the function tracer and then setting the filter to only trace functions where the process id is negative (no events), then clearing the trace buffer to ensure that we have nothing in the buffer, then write to trace_marker to add an event to the beginning of a page, sleep for 2 minutes (only 35 seconds is probably needed, but this guarantees the bug), and then finally reading the trace which will trigger the bug. This patch fixes the typo and prevents the false positive of that warning. Reported-by: Hans J. Koch <hjk@linutronix.de> Tested-by: Hans J. Koch <hjk@linutronix.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stable Kernel <stable@kernel.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-10-13 00:06:43 +08:00
#define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_EXTEND)
ring-buffer: discard timestamps that are at the start of the buffer Every buffer page in the ring buffer includes its own time stamp. When an event is recorded to the ring buffer with a delta time greater than what can be held in the event header, a time stamp event is created. If the the create timestamp falls over to the next buffer page, it is redundant because the buffer page holds a full time stamp. This patch will try to discard the time stamp when it falls to the start of the next page. This change also fixes a issues with disarding events. If most events are discarded, timestamps will start to creep into the ring buffer. If we do not discard the timestamps then they can fill up the ring buffer over time and waste space. This change will keep time stamps from filling up over another page. If something is recorded in the buffer page, and the rest is filtered, then the time stamps can only fill up to the end of the page. [ Impact: prevent time stamps from filling ring buffer ] Reported-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 21:30:10 +08:00
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
int ring_buffer_print_page_header(struct trace_seq *s)
{
struct buffer_data_page field;
int ret;
ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
tracing/events: Add 'signed' field to format files The sign info used for filters in the kernel is also useful to applications that process the trace stream. Add it to the format files and make it available to userspace. Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: rostedt@goodmis.org Cc: lizf@cn.fujitsu.com Cc: hch@infradead.org Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> LKML-Reference: <1254809398-8078-2-git-send-email-tzanussi@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-06 14:09:50 +08:00
"offset:0;\tsize:%u;\tsigned:%u;\n",
(unsigned int)sizeof(field.time_stamp),
(unsigned int)is_signed_type(u64));
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
tracing/events: Add 'signed' field to format files The sign info used for filters in the kernel is also useful to applications that process the trace stream. Add it to the format files and make it available to userspace. Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: rostedt@goodmis.org Cc: lizf@cn.fujitsu.com Cc: hch@infradead.org Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> LKML-Reference: <1254809398-8078-2-git-send-email-tzanussi@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-06 14:09:50 +08:00
"offset:%u;\tsize:%u;\tsigned:%u;\n",
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
(unsigned int)offsetof(typeof(field), commit),
tracing/events: Add 'signed' field to format files The sign info used for filters in the kernel is also useful to applications that process the trace stream. Add it to the format files and make it available to userspace. Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: rostedt@goodmis.org Cc: lizf@cn.fujitsu.com Cc: hch@infradead.org Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> LKML-Reference: <1254809398-8078-2-git-send-email-tzanussi@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-06 14:09:50 +08:00
(unsigned int)sizeof(field.commit),
(unsigned int)is_signed_type(long));
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
ret = trace_seq_printf(s, "\tfield: int overwrite;\t"
"offset:%u;\tsize:%u;\tsigned:%u;\n",
(unsigned int)offsetof(typeof(field), commit),
1,
(unsigned int)is_signed_type(long));
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
ret = trace_seq_printf(s, "\tfield: char data;\t"
tracing/events: Add 'signed' field to format files The sign info used for filters in the kernel is also useful to applications that process the trace stream. Add it to the format files and make it available to userspace. Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: rostedt@goodmis.org Cc: lizf@cn.fujitsu.com Cc: hch@infradead.org Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> LKML-Reference: <1254809398-8078-2-git-send-email-tzanussi@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-06 14:09:50 +08:00
"offset:%u;\tsize:%u;\tsigned:%u;\n",
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
(unsigned int)offsetof(typeof(field), data),
tracing/events: Add 'signed' field to format files The sign info used for filters in the kernel is also useful to applications that process the trace stream. Add it to the format files and make it available to userspace. Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: rostedt@goodmis.org Cc: lizf@cn.fujitsu.com Cc: hch@infradead.org Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> LKML-Reference: <1254809398-8078-2-git-send-email-tzanussi@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-06 14:09:50 +08:00
(unsigned int)BUF_PAGE_SIZE,
(unsigned int)is_signed_type(char));
tracing/events/ring-buffer: expose format of ring buffer headers to users Currently, every thing needed to read the binary output from the ring buffers is available, with the exception of the way the ring buffers handles itself internally. This patch creates two special files in the debugfs/tracing/events directory: # cat /debug/tracing/events/header_page field: u64 timestamp; offset:0; size:8; field: local_t commit; offset:8; size:8; field: char data; offset:16; size:4080; # cat /debug/tracing/events/header_event type : 2 bits len : 3 bits time_delta : 27 bits array : 32 bits padding : type == 0 time_extend : type == 1 data : type == 3 This is to allow a userspace app to see if the ring buffer format changes or not. [ Impact: allow userspace apps to know of ringbuffer format changes ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-16 04:53:47 +08:00
return ret;
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/*
* head_page == tail_page && head == tail then buffer is empty.
*/
struct ring_buffer_per_cpu {
int cpu;
trace: Reorder struct ring_buffer_per_cpu to remove padding on 64bit Reorder structure to remove 8 bytes of padding on 64 bit builds. This shrinks the size to 128 bytes so allowing allocation from a smaller slab & needed one fewer cache lines. Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk> LKML-Reference: <1269516456.2054.8.camel@localhost> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-25 19:27:36 +08:00
atomic_t record_disabled;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
struct ring_buffer *buffer;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
spinlock_t reader_lock; /* serialize readers */
locking: Convert raw_spinlock to arch_spinlock The raw_spin* namespace was taken by lockdep for the architecture specific implementations. raw_spin_* would be the ideal name space for the spinlocks which are not converted to sleeping locks in preempt-rt. Linus suggested to convert the raw_ to arch_ locks and cleanup the name space instead of using an artifical name like core_spin, atomic_spin or whatever No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: linux-arch@vger.kernel.org
2009-12-03 02:49:50 +08:00
arch_spinlock_t lock;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
struct lock_class_key lock_key;
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
struct list_head *pages;
ring-buffer: move page indexes into page headers Remove the global head and tail indexes and move them into the page header. Each page will now keep track of where the last write and read was made. We also rename the head and tail to read and write for better clarification. This patch is needed for future enhancements to move the ring buffer to a lockless solution. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:58 +08:00
struct buffer_page *head_page; /* read from head */
struct buffer_page *tail_page; /* write to tail */
tracing: fix typos in comments Impact: clean up. Fix typos in the comments. Signed-off-by: Wenji Huang <wenji.huang@oracle.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-10 14:03:18 +08:00
struct buffer_page *commit_page; /* committed pages */
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
struct buffer_page *reader_page;
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
unsigned long lost_events;
unsigned long last_overrun;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
local_t commit_overrun;
local_t overrun;
ring-buffer: convert cpu buffer entries to local_t The entries counter in cpu buffer is not atomic. It can be updated by other interrupts or from another CPU (readers). But making entries into "atomic_t" causes an atomic operation that can hurt performance. Instead we convert it to a local_t that will increment a counter with a local CPU atomic operation (if the arch supports it). Instead of fighting with readers and overwrites that decrement the counter, I added a "read" counter. Every time a reader reads an entry it is incremented. We already have a overrun counter and with that, the entries counter and the read counter, we can calculate the total number of entries in the buffer with: (entries - overrun) - read As long as the total number of entries in the ring buffer is less than the word size, this will work. But since the entries counter was previously a long, this is no different than what we had before. Thanks to Andrew Morton for pointing out in the first version that atomic_t does not replace unsigned long. I switched to atomic_long_t even though it is signed. A negative count is most likely a bug. [ Impact: keep accurate count of cpu buffer entries ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-01 08:49:44 +08:00
local_t entries;
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
local_t committing;
local_t commits;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
unsigned long read;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
u64 write_stamp;
u64 read_stamp;
};
struct ring_buffer {
unsigned pages;
unsigned flags;
int cpus;
atomic_t record_disabled;
ring_buffer: pahole struct ring_buffer While fixing some bugs in pahole (built-in.o files were not being processed due to relocation problems) I found out about these packable structures: $ pahole --packable kernel/trace/ring_buffer.o | grep ring ring_buffer 72 64 8 ring_buffer_per_cpu 112 104 8 If we take a look at the current layout of struct ring_buffer we can see that we have two 4 bytes holes. $ pahole -C ring_buffer kernel/trace/ring_buffer.o struct ring_buffer { unsigned int pages; /* 0 4 */ unsigned int flags; /* 4 4 */ int cpus; /* 8 4 */ /* XXX 4 bytes hole, try to pack */ cpumask_var_t cpumask; /* 16 8 */ atomic_t record_disabled; /* 24 4 */ /* XXX 4 bytes hole, try to pack */ struct mutex mutex; /* 32 32 */ /* --- cacheline 1 boundary (64 bytes) --- */ struct ring_buffer_per_cpu * * buffers; /* 64 8 */ /* size: 72, cachelines: 2, members: 7 */ /* sum members: 64, holes: 2, sum holes: 8 */ /* last cacheline: 8 bytes */ }; So, if I ask pahole to reorganize it: $ pahole -C ring_buffer --reorganize kernel/trace/ring_buffer.o struct ring_buffer { unsigned int pages; /* 0 4 */ unsigned int flags; /* 4 4 */ int cpus; /* 8 4 */ atomic_t record_disabled; /* 12 4 */ cpumask_var_t cpumask; /* 16 8 */ struct mutex mutex; /* 24 32 */ struct ring_buffer_per_cpu * * buffers; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */ /* size: 64, cachelines: 1, members: 7 */ }; /* saved 8 bytes and 1 cacheline! */ We get it using just one 64 bytes cacheline. To see what it did: $ pahole -C ring_buffer --reorganize --show_reorg_steps \ kernel/trace/ring_buffer.o | grep \/ /* Moving 'record_disabled' from after 'cpumask' to after 'cpus' */ Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-10 03:04:06 +08:00
cpumask_var_t cpumask;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: pass in lockdep class key for reader_lock On Sun, 7 Jun 2009, Ingo Molnar wrote: > Testing tracer sched_switch: <6>Starting ring buffer hammer > PASSED > Testing tracer sysprof: PASSED > Testing tracer function: PASSED > Testing tracer irqsoff: > ============================================= > PASSED > Testing tracer preemptoff: PASSED > Testing tracer preemptirqsoff: [ INFO: possible recursive locking detected ] > PASSED > Testing tracer branch: 2.6.30-rc8-tip-01972-ge5b9078-dirty #5760 > --------------------------------------------- > rb_consumer/431 is trying to acquire lock: > (&cpu_buffer->reader_lock){......}, at: [<c109eef7>] ring_buffer_reset_cpu+0x37/0x70 > > but task is already holding lock: > (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 > > other info that might help us debug this: > 1 lock held by rb_consumer/431: > #0: (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 The ring buffer is a generic structure, and can be used outside of ftrace. If ftrace traces within the use of the ring buffer, it can produce false positives with lockdep. This patch passes in a static lock key into the allocation of the ring buffer, so that different ring buffers will have their own lock class. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1244477919.13761.9042.camel@twins> [ store key in ring buffer descriptor ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-09 00:18:39 +08:00
struct lock_class_key *reader_lock_key;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
struct mutex mutex;
struct ring_buffer_per_cpu **buffers;
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
ring-buffer: use CONFIG_HOTPLUG_CPU not CONFIG_HOTPLUG The hotplug code in the ring buffers is for use with CPU hotplug, not generic hotplug. Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 23:46:03 +08:00
#ifdef CONFIG_HOTPLUG_CPU
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
struct notifier_block cpu_notify;
#endif
ring-buffer: add api to allow a tracer to change clock source This patch adds a new function called ring_buffer_set_clock that allows a tracer to assign its own clock source to the buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-18 05:22:06 +08:00
u64 (*clock)(void);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
};
struct ring_buffer_iter {
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long head;
struct buffer_page *head_page;
ring-buffer: Check if ring buffer iterator has stale data Usually reads of the ring buffer is performed by a single task. There are two types of reads from the ring buffer. One is a consuming read which will consume the entry that was read and the next read will be the entry that follows. The other is an iterator that will let the user read the contents of the ring buffer without modifying it. When an iterator is allocated, writes to the ring buffer are disabled to protect the iterator. The problem exists when consuming reads happen while an iterator is allocated. Specifically, the kind of read that swaps out an entire page (used by splice) and replaces it with a new read. If the iterator is on the page that is swapped out, then the next read may read from this swapped out page and return garbage. This patch adds a check when reading the iterator to make sure that the iterator contents are still valid. If a consuming read has taken place, the iterator is reset. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-01-26 04:17:47 +08:00
struct buffer_page *cache_reader_page;
unsigned long cache_read;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
u64 read_stamp;
};
ring-buffer: replace most bug ons with warn on and disable buffer This patch replaces most of the BUG_ONs in the ring_buffer code with RB_WARN_ON variants. It adds some more variants as needed for the replacement. This lets the buffer die nicely and still warn the user. One BUG_ON remains in the code, and that is because it detects a bad pointer passed in by the calling function, and not a bug by the ring buffer code itself. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-11 12:07:30 +08:00
/* buffer may be either ring_buffer or ring_buffer_per_cpu */
ring-buffer: disable all cpu buffers when one finds a problem Currently the way RB_WARN_ON works, is to disable either the current CPU buffer or all CPU buffers, depending on whether a ring_buffer or ring_buffer_per_cpu struct was passed into the macro. Most users of the RB_WARN_ON pass in the CPU buffer, so only the one CPU buffer gets disabled but the rest are still active. This may confuse users even though a warning is sent to the console. This patch changes the macro to disable the entire buffer even if the CPU buffer is passed in. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-04 07:53:46 +08:00
#define RB_WARN_ON(b, cond) \
({ \
int _____ret = unlikely(cond); \
if (_____ret) { \
if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
struct ring_buffer_per_cpu *__b = \
(void *)b; \
atomic_inc(&__b->buffer->record_disabled); \
} else \
atomic_inc(&b->record_disabled); \
WARN_ON(1); \
} \
_____ret; \
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
})
ring-buffer: replace most bug ons with warn on and disable buffer This patch replaces most of the BUG_ONs in the ring_buffer code with RB_WARN_ON variants. It adds some more variants as needed for the replacement. This lets the buffer die nicely and still warn the user. One BUG_ON remains in the code, and that is because it detects a bad pointer passed in by the calling function, and not a bug by the ring buffer code itself. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-11 12:07:30 +08:00
ring-buffer: add api to allow a tracer to change clock source This patch adds a new function called ring_buffer_set_clock that allows a tracer to assign its own clock source to the buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-18 05:22:06 +08:00
/* Up this if you want to test the TIME_EXTENTS and normalization */
#define DEBUG_SHIFT 0
tracing: Remove cpu arg from the rb_time_stamp() function The cpu argument is not used inside the rb_time_stamp() function. Plus fix a typo. Signed-off-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20091023233647.118547500@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-24 07:36:19 +08:00
static inline u64 rb_time_stamp(struct ring_buffer *buffer)
ring-buffer: use internal time stamp function The ring_buffer_time_stamp that is exported adds a little more overhead than is needed for using it internally. This patch adds an internal timestamp function that can be inlined (a single line function) and used internally for the ring buffer. [ Impact: a little less overhead to the ring buffer ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 04:28:23 +08:00
{
/* shift to debug/test normalization and TIME_EXTENTS */
return buffer->clock() << DEBUG_SHIFT;
}
ring-buffer: add api to allow a tracer to change clock source This patch adds a new function called ring_buffer_set_clock that allows a tracer to assign its own clock source to the buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-18 05:22:06 +08:00
u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
{
u64 time;
preempt_disable_notrace();
tracing: Remove cpu arg from the rb_time_stamp() function The cpu argument is not used inside the rb_time_stamp() function. Plus fix a typo. Signed-off-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20091023233647.118547500@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-24 07:36:19 +08:00
time = rb_time_stamp(buffer);
ring-buffer: add api to allow a tracer to change clock source This patch adds a new function called ring_buffer_set_clock that allows a tracer to assign its own clock source to the buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-18 05:22:06 +08:00
preempt_enable_no_resched_notrace();
return time;
}
EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
int cpu, u64 *ts)
{
/* Just stupid testing the normalize function and deltas */
*ts >>= DEBUG_SHIFT;
}
EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/*
* Making the ring buffer lockless makes things tricky.
* Although writes only happen on the CPU that they are on,
* and they only need to worry about interrupts. Reads can
* happen on any CPU.
*
* The reader page is always off the ring buffer, but when the
* reader finishes with a page, it needs to swap its page with
* a new one from the buffer. The reader needs to take from
* the head (writes go to the tail). But if a writer is in overwrite
* mode and wraps, it must push the head page forward.
*
* Here lies the problem.
*
* The reader must be careful to replace only the head page, and
* not another one. As described at the top of the file in the
* ASCII art, the reader sets its old page to point to the next
* page after head. It then sets the page after head to point to
* the old reader page. But if the writer moves the head page
* during this operation, the reader could end up with the tail.
*
* We use cmpxchg to help prevent this race. We also do something
* special with the page before head. We set the LSB to 1.
*
* When the writer must push the page forward, it will clear the
* bit that points to the head page, move the head, and then set
* the bit that points to the new head page.
*
* We also don't want an interrupt coming in and moving the head
* page on another writer. Thus we use the second LSB to catch
* that too. Thus:
*
* head->list->prev->next bit 1 bit 0
* ------- -------
* Normal page 0 0
* Points to head page 0 1
* New head page 1 0
*
* Note we can not trust the prev pointer of the head page, because:
*
* +----+ +-----+ +-----+
* | |------>| T |---X--->| N |
* | |<------| | | |
* +----+ +-----+ +-----+
* ^ ^ |
* | +-----+ | |
* +----------| R |----------+ |
* | |<-----------+
* +-----+
*
* Key: ---X--> HEAD flag set in pointer
* T Tail page
* R Reader page
* N Next page
*
* (see __rb_reserve_next() to see where this happens)
*
* What the above shows is that the reader just swapped out
* the reader page with a page in the buffer, but before it
* could make the new header point back to the new page added
* it was preempted by a writer. The writer moved forward onto
* the new page added by the reader and is about to move forward
* again.
*
* You can see, it is legitimate for the previous pointer of
* the head (or any page) not to point back to itself. But only
* temporarially.
*/
#define RB_PAGE_NORMAL 0UL
#define RB_PAGE_HEAD 1UL
#define RB_PAGE_UPDATE 2UL
#define RB_FLAG_MASK 3UL
/* PAGE_MOVED is not part of the mask */
#define RB_PAGE_MOVED 4UL
/*
* rb_list_head - remove any bit
*/
static struct list_head *rb_list_head(struct list_head *list)
{
unsigned long val = (unsigned long)list;
return (struct list_head *)(val & ~RB_FLAG_MASK);
}
/*
tracing: Remove cpu arg from the rb_time_stamp() function The cpu argument is not used inside the rb_time_stamp() function. Plus fix a typo. Signed-off-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20091023233647.118547500@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-24 07:36:19 +08:00
* rb_is_head_page - test if the given page is the head page
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
*
* Because the reader may move the head_page pointer, we can
* not trust what the head page is (it may be pointing to
* the reader page). But if the next page is a header page,
* its flags will be non zero.
*/
static int inline
rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *page, struct list_head *list)
{
unsigned long val;
val = (unsigned long)list->next;
if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
return RB_PAGE_MOVED;
return val & RB_FLAG_MASK;
}
/*
* rb_is_reader_page
*
* The unique thing about the reader page, is that, if the
* writer is ever on it, the previous pointer never points
* back to the reader page.
*/
static int rb_is_reader_page(struct buffer_page *page)
{
struct list_head *list = page->list.prev;
return rb_list_head(list->next) != &page->list;
}
/*
* rb_set_list_to_head - set a list_head to be pointing to head.
*/
static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
struct list_head *list)
{
unsigned long *ptr;
ptr = (unsigned long *)&list->next;
*ptr |= RB_PAGE_HEAD;
*ptr &= ~RB_PAGE_UPDATE;
}
/*
* rb_head_page_activate - sets up head page
*/
static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *head;
head = cpu_buffer->head_page;
if (!head)
return;
/*
* Set the previous list pointer to have the HEAD flag.
*/
rb_set_list_to_head(cpu_buffer, head->list.prev);
}
static void rb_list_head_clear(struct list_head *list)
{
unsigned long *ptr = (unsigned long *)&list->next;
*ptr &= ~RB_FLAG_MASK;
}
/*
* rb_head_page_dactivate - clears head page ptr (for free list)
*/
static void
rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
{
struct list_head *hd;
/* Go through the whole list and clear any pointers found. */
rb_list_head_clear(cpu_buffer->pages);
list_for_each(hd, cpu_buffer->pages)
rb_list_head_clear(hd);
}
static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *head,
struct buffer_page *prev,
int old_flag, int new_flag)
{
struct list_head *list;
unsigned long val = (unsigned long)&head->list;
unsigned long ret;
list = &prev->list;
val &= ~RB_FLAG_MASK;
ring-buffer: typecast cmpxchg to fix PowerPC warning The cmpxchg used by PowerPC does the following: ({ \ __typeof__(*(ptr)) _o_ = (o); \ __typeof__(*(ptr)) _n_ = (n); \ (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_, \ (unsigned long)_n_, sizeof(*(ptr))); \ }) This does a type check of *ptr to both o and n. Unfortunately, the code in ring-buffer.c assigns longs to pointers and pointers to longs and causes a warning on PowerPC: ring_buffer.c: In function 'rb_head_page_set': ring_buffer.c:704: warning: initialization makes pointer from integer without a cast ring_buffer.c:704: warning: initialization makes pointer from integer without a cast ring_buffer.c: In function 'rb_head_page_replace': ring_buffer.c:797: warning: initialization makes integer from pointer without a cast This patch adds the typecasts inside cmpxchg to annotate that a long is being cast to a pointer and a pointer is being casted to a long and this removes the PowerPC warnings. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-14 21:31:35 +08:00
ret = cmpxchg((unsigned long *)&list->next,
val | old_flag, val | new_flag);
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/* check if the reader took the page */
if ((ret & ~RB_FLAG_MASK) != val)
return RB_PAGE_MOVED;
return ret & RB_FLAG_MASK;
}
static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *head,
struct buffer_page *prev,
int old_flag)
{
return rb_head_page_set(cpu_buffer, head, prev,
old_flag, RB_PAGE_UPDATE);
}
static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *head,
struct buffer_page *prev,
int old_flag)
{
return rb_head_page_set(cpu_buffer, head, prev,
old_flag, RB_PAGE_HEAD);
}
static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *head,
struct buffer_page *prev,
int old_flag)
{
return rb_head_page_set(cpu_buffer, head, prev,
old_flag, RB_PAGE_NORMAL);
}
static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page **bpage)
{
struct list_head *p = rb_list_head((*bpage)->list.next);
*bpage = list_entry(p, struct buffer_page, list);
}
static struct buffer_page *
rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *head;
struct buffer_page *page;
struct list_head *list;
int i;
if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
return NULL;
/* sanity check */
list = cpu_buffer->pages;
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
return NULL;
page = head = cpu_buffer->head_page;
/*
* It is possible that the writer moves the header behind
* where we started, and we miss in one loop.
* A second loop should grab the header, but we'll do
* three loops just because I'm paranoid.
*/
for (i = 0; i < 3; i++) {
do {
if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
cpu_buffer->head_page = page;
return page;
}
rb_inc_page(cpu_buffer, &page);
} while (page != head);
}
RB_WARN_ON(cpu_buffer, 1);
return NULL;
}
static int rb_head_page_replace(struct buffer_page *old,
struct buffer_page *new)
{
unsigned long *ptr = (unsigned long *)&old->list.prev->next;
unsigned long val;
unsigned long ret;
val = *ptr & ~RB_FLAG_MASK;
val |= RB_PAGE_HEAD;
ring-buffer: typecast cmpxchg to fix PowerPC warning The cmpxchg used by PowerPC does the following: ({ \ __typeof__(*(ptr)) _o_ = (o); \ __typeof__(*(ptr)) _n_ = (n); \ (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_, \ (unsigned long)_n_, sizeof(*(ptr))); \ }) This does a type check of *ptr to both o and n. Unfortunately, the code in ring-buffer.c assigns longs to pointers and pointers to longs and causes a warning on PowerPC: ring_buffer.c: In function 'rb_head_page_set': ring_buffer.c:704: warning: initialization makes pointer from integer without a cast ring_buffer.c:704: warning: initialization makes pointer from integer without a cast ring_buffer.c: In function 'rb_head_page_replace': ring_buffer.c:797: warning: initialization makes integer from pointer without a cast This patch adds the typecasts inside cmpxchg to annotate that a long is being cast to a pointer and a pointer is being casted to a long and this removes the PowerPC warnings. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-14 21:31:35 +08:00
ret = cmpxchg(ptr, val, (unsigned long)&new->list);
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
return ret == val;
}
/*
* rb_tail_page_update - move the tail page forward
*
* Returns 1 if moved tail page, 0 if someone else did.
*/
static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *tail_page,
struct buffer_page *next_page)
{
struct buffer_page *old_tail;
unsigned long old_entries;
unsigned long old_write;
int ret = 0;
/*
* The tail page now needs to be moved forward.
*
* We need to reset the tail page, but without messing
* with possible erasing of data brought in by interrupts
* that have moved the tail page and are currently on it.
*
* We add a counter to the write field to denote this.
*/
old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
/*
* Just make sure we have seen our old_write and synchronize
* with any interrupts that come in.
*/
barrier();
/*
* If the tail page is still the same as what we think
* it is, then it is up to us to update the tail
* pointer.
*/
if (tail_page == cpu_buffer->tail_page) {
/* Zero the write counter */
unsigned long val = old_write & ~RB_WRITE_MASK;
unsigned long eval = old_entries & ~RB_WRITE_MASK;
/*
* This will only succeed if an interrupt did
* not come in and change it. In which case, we
* do not want to modify it.
ring_buffer: Fix warning while ignoring cmpxchg return value kernel/trace/ring_buffer.c: In function 'rb_tail_page_update': kernel/trace/ring_buffer.c:849: warning: value computed is not used kernel/trace/ring_buffer.c:850: warning: value computed is not used Add "(void)"s to fix this warning, because we don't need here to handle the fail case of cmpxchg, it's fine if an interrupt already did the job. Changed from V1: Add a comment(which is written by Steven) for it. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2009-07-15 16:27:30 +08:00
*
* We add (void) to let the compiler know that we do not care
* about the return value of these functions. We use the
* cmpxchg to only update if an interrupt did not already
* do it for us. If the cmpxchg fails, we don't care.
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
*/
ring_buffer: Fix warning while ignoring cmpxchg return value kernel/trace/ring_buffer.c: In function 'rb_tail_page_update': kernel/trace/ring_buffer.c:849: warning: value computed is not used kernel/trace/ring_buffer.c:850: warning: value computed is not used Add "(void)"s to fix this warning, because we don't need here to handle the fail case of cmpxchg, it's fine if an interrupt already did the job. Changed from V1: Add a comment(which is written by Steven) for it. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2009-07-15 16:27:30 +08:00
(void)local_cmpxchg(&next_page->write, old_write, val);
(void)local_cmpxchg(&next_page->entries, old_entries, eval);
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/*
* No need to worry about races with clearing out the commit.
* it only can increment when a commit takes place. But that
* only happens in the outer most nested commit.
*/
local_set(&next_page->page->commit, 0);
old_tail = cmpxchg(&cpu_buffer->tail_page,
tail_page, next_page);
if (old_tail == tail_page)
ret = 1;
}
return ret;
}
static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *bpage)
{
unsigned long val = (unsigned long)bpage;
if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
return 1;
return 0;
}
/**
* rb_check_list - make sure a pointer to a list has the last bits zero
*/
static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
struct list_head *list)
{
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
return 1;
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
return 1;
return 0;
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* check_pages - integrity check of buffer pages
* @cpu_buffer: CPU buffer with pages to test
*
tracing: fix typos in comments Impact: clean up. Fix typos in the comments. Signed-off-by: Wenji Huang <wenji.huang@oracle.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-10 14:03:18 +08:00
* As a safety measure we check to make sure the data pages have not
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
* been corrupted.
*/
static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
{
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
struct list_head *head = cpu_buffer->pages;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
struct buffer_page *bpage, *tmp;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_head_page_deactivate(cpu_buffer);
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
return -1;
if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
return -1;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
if (rb_check_list(cpu_buffer, head))
return -1;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
list_for_each_entry_safe(bpage, tmp, head, list) {
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
if (RB_WARN_ON(cpu_buffer,
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage->list.next->prev != &bpage->list))
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
return -1;
if (RB_WARN_ON(cpu_buffer,
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage->list.prev->next != &bpage->list))
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
return -1;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
if (rb_check_list(cpu_buffer, &bpage->list))
return -1;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_head_page_activate(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return 0;
}
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
unsigned nr_pages)
{
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
struct buffer_page *bpage, *tmp;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
unsigned long addr;
LIST_HEAD(pages);
unsigned i;
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
WARN_ON(!nr_pages);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
for (i = 0; i < nr_pages; i++) {
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
ring_buffer: map to cpu not page My original patch had a compile bug when NUMA was configured. I referenced cpu when it should have been cpu_buffer->cpu. Ingo quickly fixed this bug by replacing cpu with 'i' because that was the loop counter. Unfortunately, the 'i' was the counter of pages, not CPUs. This caused a crash when the number of pages allocated for the buffers exceeded the number of pages, which would usually be the case. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-03 07:18:09 +08:00
GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
if (!bpage)
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
goto free_pages;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_check_bpage(cpu_buffer, bpage);
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
list_add(&bpage->list, &pages);
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
addr = __get_free_page(GFP_KERNEL);
if (!addr)
goto free_pages;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage->page = (void *)addr;
rb_init_page(bpage->page);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
/*
* The ring buffer page list is a circular list that does not
* start and end with a list head. All page list items point to
* other pages.
*/
cpu_buffer->pages = pages.next;
list_del(&pages);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
rb_check_pages(cpu_buffer);
return 0;
free_pages:
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
list_for_each_entry_safe(bpage, tmp, &pages, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
return -ENOMEM;
}
static struct ring_buffer_per_cpu *
rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
struct buffer_page *bpage;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
unsigned long addr;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
int ret;
cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
GFP_KERNEL, cpu_to_node(cpu));
if (!cpu_buffer)
return NULL;
cpu_buffer->cpu = cpu;
cpu_buffer->buffer = buffer;
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
spin_lock_init(&cpu_buffer->reader_lock);
ring-buffer: pass in lockdep class key for reader_lock On Sun, 7 Jun 2009, Ingo Molnar wrote: > Testing tracer sched_switch: <6>Starting ring buffer hammer > PASSED > Testing tracer sysprof: PASSED > Testing tracer function: PASSED > Testing tracer irqsoff: > ============================================= > PASSED > Testing tracer preemptoff: PASSED > Testing tracer preemptirqsoff: [ INFO: possible recursive locking detected ] > PASSED > Testing tracer branch: 2.6.30-rc8-tip-01972-ge5b9078-dirty #5760 > --------------------------------------------- > rb_consumer/431 is trying to acquire lock: > (&cpu_buffer->reader_lock){......}, at: [<c109eef7>] ring_buffer_reset_cpu+0x37/0x70 > > but task is already holding lock: > (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 > > other info that might help us debug this: > 1 lock held by rb_consumer/431: > #0: (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 The ring buffer is a generic structure, and can be used outside of ftrace. If ftrace traces within the use of the ring buffer, it can produce false positives with lockdep. This patch passes in a static lock key into the allocation of the ring buffer, so that different ring buffers will have their own lock class. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1244477919.13761.9042.camel@twins> [ store key in ring buffer descriptor ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-09 00:18:39 +08:00
lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
locking: Rename __RAW_SPIN_LOCK_UNLOCKED to __ARCH_SPIN_LOCK_UNLOCKED Further name space cleanup. No functional change Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: linux-arch@vger.kernel.org
2009-12-03 19:38:57 +08:00
cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
GFP_KERNEL, cpu_to_node(cpu));
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
if (!bpage)
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
goto fail_free_buffer;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_check_bpage(cpu_buffer, bpage);
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
cpu_buffer->reader_page = bpage;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
addr = __get_free_page(GFP_KERNEL);
if (!addr)
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
goto fail_free_reader;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage->page = (void *)addr;
rb_init_page(bpage->page);
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ret = rb_allocate_pages(cpu_buffer, buffer->pages);
if (ret < 0)
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
goto fail_free_reader;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer->head_page
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
= list_entry(cpu_buffer->pages, struct buffer_page, list);
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_head_page_activate(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return cpu_buffer;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
fail_free_reader:
free_buffer_page(cpu_buffer->reader_page);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
fail_free_buffer:
kfree(cpu_buffer);
return NULL;
}
static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
{
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
struct list_head *head = cpu_buffer->pages;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
struct buffer_page *bpage, *tmp;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
free_buffer_page(cpu_buffer->reader_page);
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_head_page_deactivate(cpu_buffer);
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
if (head) {
list_for_each_entry_safe(bpage, tmp, head, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
bpage = list_entry(head, struct buffer_page, list);
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
free_buffer_page(bpage);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
kfree(cpu_buffer);
}
ring-buffer: use CONFIG_HOTPLUG_CPU not CONFIG_HOTPLUG The hotplug code in the ring buffers is for use with CPU hotplug, not generic hotplug. Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 23:46:03 +08:00
#ifdef CONFIG_HOTPLUG_CPU
tracing/ring-buffer: don't annotate rb_cpu_notify with __cpuinit Impact: remove a section warning CONFIG_DEBUG_SECTION_MISMATCH raises the following warning on -tip: WARNING: kernel/trace/built-in.o(.text+0x5bc5): Section mismatch in reference from the function ring_buffer_alloc() to the function .cpuinit.text:rb_cpu_notify() The function ring_buffer_alloc() references the function __cpuinit rb_cpu_notify(). This is actually harmless. The code in the ring buffer don't build rb_cpu_notify and other cpu hotplug stuffs when !CONFIG_HOTPLUG_CPU so we have no risk to reference freed memory here (it would even be harmless if we unconditionally build it because register_cpu_notifier would do nothing when !CONFIG_HOTPLUG_CPU. But since ring_buffer_alloc() can be called everytime, we don't want it to be annotated with __cpuinit so we drop the __cpuinit from rb_cpu_notify. This is not a waste of memory because it is only defined and used on CONFIG_HOTPLUG_CPU. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <1237606416-22268-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-21 11:33:36 +08:00
static int rb_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
#endif
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_alloc - allocate a new ring_buffer
ring_buffer: update description for ring_buffer_alloc() Trivial patch. Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Robert Richter <robert.richter@amd.com>
2008-11-24 19:24:12 +08:00
* @size: the size in bytes per cpu that is needed.
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
* @flags: attributes to set for the ring buffer.
*
* Currently the only flag that is available is the RB_FL_OVERWRITE
* flag. This flag means that the buffer will overwrite old data
* when the buffer wraps. If this flag is not set, the buffer will
* drop data when the tail hits the head.
*/
ring-buffer: pass in lockdep class key for reader_lock On Sun, 7 Jun 2009, Ingo Molnar wrote: > Testing tracer sched_switch: <6>Starting ring buffer hammer > PASSED > Testing tracer sysprof: PASSED > Testing tracer function: PASSED > Testing tracer irqsoff: > ============================================= > PASSED > Testing tracer preemptoff: PASSED > Testing tracer preemptirqsoff: [ INFO: possible recursive locking detected ] > PASSED > Testing tracer branch: 2.6.30-rc8-tip-01972-ge5b9078-dirty #5760 > --------------------------------------------- > rb_consumer/431 is trying to acquire lock: > (&cpu_buffer->reader_lock){......}, at: [<c109eef7>] ring_buffer_reset_cpu+0x37/0x70 > > but task is already holding lock: > (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 > > other info that might help us debug this: > 1 lock held by rb_consumer/431: > #0: (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 The ring buffer is a generic structure, and can be used outside of ftrace. If ftrace traces within the use of the ring buffer, it can produce false positives with lockdep. This patch passes in a static lock key into the allocation of the ring buffer, so that different ring buffers will have their own lock class. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1244477919.13761.9042.camel@twins> [ store key in ring buffer descriptor ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-09 00:18:39 +08:00
struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
struct lock_class_key *key)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
struct ring_buffer *buffer;
int bsize;
int cpu;
/* keep it in its own cache line */
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
GFP_KERNEL);
if (!buffer)
return NULL;
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
goto fail_free_buffer;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
buffer->flags = flags;
ring-buffer: add api to allow a tracer to change clock source This patch adds a new function called ring_buffer_set_clock that allows a tracer to assign its own clock source to the buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-18 05:22:06 +08:00
buffer->clock = trace_clock_local;
ring-buffer: pass in lockdep class key for reader_lock On Sun, 7 Jun 2009, Ingo Molnar wrote: > Testing tracer sched_switch: <6>Starting ring buffer hammer > PASSED > Testing tracer sysprof: PASSED > Testing tracer function: PASSED > Testing tracer irqsoff: > ============================================= > PASSED > Testing tracer preemptoff: PASSED > Testing tracer preemptirqsoff: [ INFO: possible recursive locking detected ] > PASSED > Testing tracer branch: 2.6.30-rc8-tip-01972-ge5b9078-dirty #5760 > --------------------------------------------- > rb_consumer/431 is trying to acquire lock: > (&cpu_buffer->reader_lock){......}, at: [<c109eef7>] ring_buffer_reset_cpu+0x37/0x70 > > but task is already holding lock: > (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 > > other info that might help us debug this: > 1 lock held by rb_consumer/431: > #0: (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 The ring buffer is a generic structure, and can be used outside of ftrace. If ftrace traces within the use of the ring buffer, it can produce false positives with lockdep. This patch passes in a static lock key into the allocation of the ring buffer, so that different ring buffers will have their own lock class. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1244477919.13761.9042.camel@twins> [ store key in ring buffer descriptor ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-09 00:18:39 +08:00
buffer->reader_lock_key = key;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/* need at least two pages */
ring-buffer: check for less than two in size allocation The ring buffer must have at least two pages allocated for the reader page swap to work. The page count check will miss the case of a zero size passed in. Even though a zero size ring buffer would probably fail an allocation, making the min size check for less than two instead of equal to one makes the code a bit more robust. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-18 02:11:10 +08:00
if (buffer->pages < 2)
buffer->pages = 2;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
tracing/ring-buffer: fix non cpu hotplug case Impact: fix warning with irqsoff tracer The ring buffer allocates its buffers on pre-smp time (early_initcall). It means that, at first, only the boot cpu buffer is allocated and the ring-buffer cpumask only has the boot cpu set (cpu_online_mask). Later, the secondary cpu will show up and the ring-buffer will be notified about this event: the appropriate buffer will be allocated and the cpumask will be updated. Unfortunately, if !CONFIG_CPU_HOTPLUG, the ring-buffer will not be notified about the secondary cpus, meaning that the cpumask will have only the cpu boot set, and only one cpu buffer allocated. We fix that by using cpu_possible_mask if !CONFIG_CPU_HOTPLUG. This patch fixes the following warning with irqsoff tracer running: [ 169.317794] WARNING: at kernel/trace/trace.c:466 update_max_tr_single+0xcc/0xf3() [ 169.318002] Hardware name: AMILO Li 2727 [ 169.318002] Modules linked in: [ 169.318002] Pid: 5624, comm: bash Not tainted 2.6.29-rc8-tip-02636-g6aafa6c #11 [ 169.318002] Call Trace: [ 169.318002] [<ffffffff81036182>] warn_slowpath+0xea/0x13d [ 169.318002] [<ffffffff8100b9d6>] ? ftrace_call+0x5/0x2b [ 169.318002] [<ffffffff8100b9d6>] ? ftrace_call+0x5/0x2b [ 169.318002] [<ffffffff8100b9d1>] ? ftrace_call+0x0/0x2b [ 169.318002] [<ffffffff8101ef10>] ? ftrace_modify_code+0xa9/0x108 [ 169.318002] [<ffffffff8106e27f>] ? trace_hardirqs_off+0x25/0x27 [ 169.318002] [<ffffffff8149afe7>] ? _spin_unlock_irqrestore+0x1f/0x2d [ 169.318002] [<ffffffff81064f52>] ? ring_buffer_reset_cpu+0xf6/0xfb [ 169.318002] [<ffffffff8106637c>] ? ring_buffer_reset+0x36/0x48 [ 169.318002] [<ffffffff8106aeda>] update_max_tr_single+0xcc/0xf3 [ 169.318002] [<ffffffff8100bc17>] ? sysret_check+0x22/0x5d [ 169.318002] [<ffffffff8106e3ea>] stop_critical_timing+0x142/0x204 [ 169.318002] [<ffffffff8106e4cf>] trace_hardirqs_on_caller+0x23/0x25 [ 169.318002] [<ffffffff8149ac28>] trace_hardirqs_on_thunk+0x3a/0x3c [ 169.318002] [<ffffffff8100bc17>] ? sysret_check+0x22/0x5d [ 169.318002] ---[ end trace db76cbf775a750cf ]--- Because this tracer may try to swap two cpu ring buffers for an unregistered cpu on the ring buffer. This patch might also fix a fair loss of traces due to unallocated buffers for secondary cpus. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-b: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <1237470453-5427-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-19 21:47:33 +08:00
/*
* In case of non-hotplug cpu, if the ring-buffer is allocated
* in early initcall, it will not be notified of secondary cpus.
* In that off case, we need to allocate for all possible cpus.
*/
#ifdef CONFIG_HOTPLUG_CPU
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
get_online_cpus();
cpumask_copy(buffer->cpumask, cpu_online_mask);
tracing/ring-buffer: fix non cpu hotplug case Impact: fix warning with irqsoff tracer The ring buffer allocates its buffers on pre-smp time (early_initcall). It means that, at first, only the boot cpu buffer is allocated and the ring-buffer cpumask only has the boot cpu set (cpu_online_mask). Later, the secondary cpu will show up and the ring-buffer will be notified about this event: the appropriate buffer will be allocated and the cpumask will be updated. Unfortunately, if !CONFIG_CPU_HOTPLUG, the ring-buffer will not be notified about the secondary cpus, meaning that the cpumask will have only the cpu boot set, and only one cpu buffer allocated. We fix that by using cpu_possible_mask if !CONFIG_CPU_HOTPLUG. This patch fixes the following warning with irqsoff tracer running: [ 169.317794] WARNING: at kernel/trace/trace.c:466 update_max_tr_single+0xcc/0xf3() [ 169.318002] Hardware name: AMILO Li 2727 [ 169.318002] Modules linked in: [ 169.318002] Pid: 5624, comm: bash Not tainted 2.6.29-rc8-tip-02636-g6aafa6c #11 [ 169.318002] Call Trace: [ 169.318002] [<ffffffff81036182>] warn_slowpath+0xea/0x13d [ 169.318002] [<ffffffff8100b9d6>] ? ftrace_call+0x5/0x2b [ 169.318002] [<ffffffff8100b9d6>] ? ftrace_call+0x5/0x2b [ 169.318002] [<ffffffff8100b9d1>] ? ftrace_call+0x0/0x2b [ 169.318002] [<ffffffff8101ef10>] ? ftrace_modify_code+0xa9/0x108 [ 169.318002] [<ffffffff8106e27f>] ? trace_hardirqs_off+0x25/0x27 [ 169.318002] [<ffffffff8149afe7>] ? _spin_unlock_irqrestore+0x1f/0x2d [ 169.318002] [<ffffffff81064f52>] ? ring_buffer_reset_cpu+0xf6/0xfb [ 169.318002] [<ffffffff8106637c>] ? ring_buffer_reset+0x36/0x48 [ 169.318002] [<ffffffff8106aeda>] update_max_tr_single+0xcc/0xf3 [ 169.318002] [<ffffffff8100bc17>] ? sysret_check+0x22/0x5d [ 169.318002] [<ffffffff8106e3ea>] stop_critical_timing+0x142/0x204 [ 169.318002] [<ffffffff8106e4cf>] trace_hardirqs_on_caller+0x23/0x25 [ 169.318002] [<ffffffff8149ac28>] trace_hardirqs_on_thunk+0x3a/0x3c [ 169.318002] [<ffffffff8100bc17>] ? sysret_check+0x22/0x5d [ 169.318002] ---[ end trace db76cbf775a750cf ]--- Because this tracer may try to swap two cpu ring buffers for an unregistered cpu on the ring buffer. This patch might also fix a fair loss of traces due to unallocated buffers for secondary cpus. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-b: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <1237470453-5427-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-19 21:47:33 +08:00
#else
cpumask_copy(buffer->cpumask, cpu_possible_mask);
#endif
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
buffer->cpus = nr_cpu_ids;
bsize = sizeof(void *) * nr_cpu_ids;
buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
GFP_KERNEL);
if (!buffer->buffers)
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
goto fail_free_cpumask;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
for_each_buffer_cpu(buffer, cpu) {
buffer->buffers[cpu] =
rb_allocate_cpu_buffer(buffer, cpu);
if (!buffer->buffers[cpu])
goto fail_free_buffers;
}
ring-buffer: use CONFIG_HOTPLUG_CPU not CONFIG_HOTPLUG The hotplug code in the ring buffers is for use with CPU hotplug, not generic hotplug. Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 23:46:03 +08:00
#ifdef CONFIG_HOTPLUG_CPU
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
buffer->cpu_notify.notifier_call = rb_cpu_notify;
buffer->cpu_notify.priority = 0;
register_cpu_notifier(&buffer->cpu_notify);
#endif
put_online_cpus();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
mutex_init(&buffer->mutex);
return buffer;
fail_free_buffers:
for_each_buffer_cpu(buffer, cpu) {
if (buffer->buffers[cpu])
rb_free_cpu_buffer(buffer->buffers[cpu]);
}
kfree(buffer->buffers);
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
fail_free_cpumask:
free_cpumask_var(buffer->cpumask);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
put_online_cpus();
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
fail_free_buffer:
kfree(buffer);
return NULL;
}
ring-buffer: pass in lockdep class key for reader_lock On Sun, 7 Jun 2009, Ingo Molnar wrote: > Testing tracer sched_switch: <6>Starting ring buffer hammer > PASSED > Testing tracer sysprof: PASSED > Testing tracer function: PASSED > Testing tracer irqsoff: > ============================================= > PASSED > Testing tracer preemptoff: PASSED > Testing tracer preemptirqsoff: [ INFO: possible recursive locking detected ] > PASSED > Testing tracer branch: 2.6.30-rc8-tip-01972-ge5b9078-dirty #5760 > --------------------------------------------- > rb_consumer/431 is trying to acquire lock: > (&cpu_buffer->reader_lock){......}, at: [<c109eef7>] ring_buffer_reset_cpu+0x37/0x70 > > but task is already holding lock: > (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 > > other info that might help us debug this: > 1 lock held by rb_consumer/431: > #0: (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0 The ring buffer is a generic structure, and can be used outside of ftrace. If ftrace traces within the use of the ring buffer, it can produce false positives with lockdep. This patch passes in a static lock key into the allocation of the ring buffer, so that different ring buffers will have their own lock class. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1244477919.13761.9042.camel@twins> [ store key in ring buffer descriptor ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-09 00:18:39 +08:00
EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_free - free a ring buffer.
* @buffer: the buffer to free.
*/
void
ring_buffer_free(struct ring_buffer *buffer)
{
int cpu;
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
get_online_cpus();
ring-buffer: use CONFIG_HOTPLUG_CPU not CONFIG_HOTPLUG The hotplug code in the ring buffers is for use with CPU hotplug, not generic hotplug. Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 23:46:03 +08:00
#ifdef CONFIG_HOTPLUG_CPU
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
unregister_cpu_notifier(&buffer->cpu_notify);
#endif
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
for_each_buffer_cpu(buffer, cpu)
rb_free_cpu_buffer(buffer->buffers[cpu]);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
put_online_cpus();
ring-buffer: Fix memleak in ring_buffer_free() I noticed oprofile memleaked in linux-2.6 current tree, and tracked this ring-buffer leak. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> LKML-Reference: <4A7C06B9.2090302@gmail.com> Cc: stable@kernel.org Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-08-07 18:49:29 +08:00
kfree(buffer->buffers);
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
free_cpumask_var(buffer->cpumask);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
kfree(buffer);
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_free);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: add api to allow a tracer to change clock source This patch adds a new function called ring_buffer_set_clock that allows a tracer to assign its own clock source to the buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-18 05:22:06 +08:00
void ring_buffer_set_clock(struct ring_buffer *buffer,
u64 (*clock)(void))
{
buffer->clock = clock;
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
static void
rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
{
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
struct buffer_page *bpage;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
struct list_head *p;
unsigned i;
ring-buffer: Synchronize resizing buffer with reader lock We got a sudden panic when we reduced the size of the ringbuffer. We can reproduce the panic by the following steps: echo 1 > events/sched/enable cat trace_pipe > /dev/null & while ((1)) do echo 12000 > buffer_size_kb echo 512 > buffer_size_kb done (not more than 5 seconds, panic ...) Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <4AF01735.9060409@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-11-03 19:42:45 +08:00
spin_lock_irq(&cpu_buffer->reader_lock);
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_head_page_deactivate(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
for (i = 0; i < nr_pages; i++) {
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
ring-buffer: Add missing unlock In some error handling cases the lock is not unlocked. The return is converted to a goto, to share the unlock at the end of the function. A simplified version of the semantic patch that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @r exists@ expression E1; identifier f; @@ f (...) { <+... * spin_lock_irq (E1,...); ... when != E1 * return ...; ...+> } // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> LKML-Reference: <Pine.LNX.4.64.1003291736440.21896@ask.diku.dk> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-29 23:37:02 +08:00
goto out;
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
p = cpu_buffer->pages->next;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage = list_entry(p, struct buffer_page, list);
list_del_init(&bpage->list);
free_buffer_page(bpage);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
ring-buffer: Add missing unlock In some error handling cases the lock is not unlocked. The return is converted to a goto, to share the unlock at the end of the function. A simplified version of the semantic patch that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @r exists@ expression E1; identifier f; @@ f (...) { <+... * spin_lock_irq (E1,...); ... when != E1 * return ...; ...+> } // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> LKML-Reference: <Pine.LNX.4.64.1003291736440.21896@ask.diku.dk> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-29 23:37:02 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
rb_reset_cpu(cpu_buffer);
rb_check_pages(cpu_buffer);
ring-buffer: Add missing unlock In some error handling cases the lock is not unlocked. The return is converted to a goto, to share the unlock at the end of the function. A simplified version of the semantic patch that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @r exists@ expression E1; identifier f; @@ f (...) { <+... * spin_lock_irq (E1,...); ... when != E1 * return ...; ...+> } // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> LKML-Reference: <Pine.LNX.4.64.1003291736440.21896@ask.diku.dk> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-29 23:37:02 +08:00
out:
ring-buffer: Move resize integrity check under reader lock While using an application that does splice on the ftrace ring buffer at start up, I triggered an integrity check failure. Looking into this, I discovered that resizing the buffer performs an integrity check after the buffer is resized. This check unfortunately is preformed after it releases the reader lock. If a reader is reading the buffer it may cause the integrity check to trigger a false failure. This patch simply moves the integrity checker under the protection of the ring buffer reader lock. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-12-11 12:20:52 +08:00
spin_unlock_irq(&cpu_buffer->reader_lock);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
static void
rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
struct list_head *pages, unsigned nr_pages)
{
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
struct buffer_page *bpage;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
struct list_head *p;
unsigned i;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
spin_lock_irq(&cpu_buffer->reader_lock);
rb_head_page_deactivate(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
for (i = 0; i < nr_pages; i++) {
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
ring-buffer: Add missing unlock In some error handling cases the lock is not unlocked. The return is converted to a goto, to share the unlock at the end of the function. A simplified version of the semantic patch that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @r exists@ expression E1; identifier f; @@ f (...) { <+... * spin_lock_irq (E1,...); ... when != E1 * return ...; ...+> } // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> LKML-Reference: <Pine.LNX.4.64.1003291736440.21896@ask.diku.dk> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-29 23:37:02 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
p = pages->next;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage = list_entry(p, struct buffer_page, list);
list_del_init(&bpage->list);
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
list_add_tail(&bpage->list, cpu_buffer->pages);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
rb_reset_cpu(cpu_buffer);
rb_check_pages(cpu_buffer);
ring-buffer: Add missing unlock In some error handling cases the lock is not unlocked. The return is converted to a goto, to share the unlock at the end of the function. A simplified version of the semantic patch that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @r exists@ expression E1; identifier f; @@ f (...) { <+... * spin_lock_irq (E1,...); ... when != E1 * return ...; ...+> } // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> LKML-Reference: <Pine.LNX.4.64.1003291736440.21896@ask.diku.dk> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-29 23:37:02 +08:00
out:
ring-buffer: Move resize integrity check under reader lock While using an application that does splice on the ftrace ring buffer at start up, I triggered an integrity check failure. Looking into this, I discovered that resizing the buffer performs an integrity check after the buffer is resized. This check unfortunately is preformed after it releases the reader lock. If a reader is reading the buffer it may cause the integrity check to trigger a false failure. This patch simply moves the integrity checker under the protection of the ring buffer reader lock. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-12-11 12:20:52 +08:00
spin_unlock_irq(&cpu_buffer->reader_lock);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
/**
* ring_buffer_resize - resize the ring buffer
* @buffer: the buffer to resize.
* @size: the new size.
*
* Minimum size is 2 * BUF_PAGE_SIZE.
*
* Returns -1 on failure.
*/
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned nr_pages, rm_pages, new_pages;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
struct buffer_page *bpage, *tmp;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
unsigned long buffer_size;
unsigned long addr;
LIST_HEAD(pages);
int i, cpu;
tracing: fix mmiotrace resizing crash Pekka reported a crash when resizing the mmiotrace tracer (if only mmiotrace is enabled). This happens because in that case we do not allocate the max buffer, but we try to use it. Make ring_buffer_resize() idempotent against NULL buffers. Reported-by: Pekka Paalanen <pq@iki.fi> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-13 21:58:31 +08:00
/*
* Always succeed at resizing a non-existent buffer:
*/
if (!buffer)
return size;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
size *= BUF_PAGE_SIZE;
buffer_size = buffer->pages * BUF_PAGE_SIZE;
/* we need a minimum of two pages */
if (size < BUF_PAGE_SIZE * 2)
size = BUF_PAGE_SIZE * 2;
if (size == buffer_size)
return size;
ring-buffer: Use sync sched protection on ring buffer resizing There was a comment in the ring buffer code that says the calling layers should prevent tracing or reading of the ring buffer while resizing. I have discovered that the tracers do not honor this arrangement. This patch moves the disabling and synchronizing the ring buffer to a higher layer during resizing. This guarantees that no writes are occurring while the resize takes place. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-12-11 11:54:27 +08:00
atomic_inc(&buffer->record_disabled);
/* Make sure all writers are done with this buffer. */
synchronize_sched();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
mutex_lock(&buffer->mutex);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
get_online_cpus();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
if (size < buffer_size) {
/* easy case, just free pages */
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
goto out_fail;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
rm_pages = buffer->pages - nr_pages;
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
rb_remove_pages(cpu_buffer, rm_pages);
}
goto out;
}
/*
* This is a bit more difficult. We only want to add pages
* when we can allocate enough for all CPUs. We do this
* by allocating all the pages and storing them on a local
* link list. If we succeed in our allocation, then we
* add these pages to the cpu_buffers. Otherwise we just free
* them all and return -ENOMEM;
*/
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
goto out_fail;
ring-buffer: replace most bug ons with warn on and disable buffer This patch replaces most of the BUG_ONs in the ring_buffer code with RB_WARN_ON variants. It adds some more variants as needed for the replacement. This lets the buffer die nicely and still warn the user. One BUG_ON remains in the code, and that is because it detects a bad pointer passed in by the calling function, and not a bug by the ring buffer code itself. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-11 12:07:30 +08:00
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
new_pages = nr_pages - buffer->pages;
for_each_buffer_cpu(buffer, cpu) {
for (i = 0; i < new_pages; i++) {
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage = kzalloc_node(ALIGN(sizeof(*bpage),
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
cache_line_size()),
GFP_KERNEL, cpu_to_node(cpu));
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
if (!bpage)
ring_buffer: allocate buffer page pointer The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 23:14:54 +08:00
goto free_pages;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
list_add(&bpage->list, &pages);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
addr = __get_free_page(GFP_KERNEL);
if (!addr)
goto free_pages;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage->page = (void *)addr;
rb_init_page(bpage->page);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
}
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
rb_insert_pages(cpu_buffer, &pages, new_pages);
}
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
if (RB_WARN_ON(buffer, !list_empty(&pages)))
goto out_fail;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
out:
buffer->pages = nr_pages;
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
put_online_cpus();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
mutex_unlock(&buffer->mutex);
ring-buffer: Use sync sched protection on ring buffer resizing There was a comment in the ring buffer code that says the calling layers should prevent tracing or reading of the ring buffer while resizing. I have discovered that the tracers do not honor this arrangement. This patch moves the disabling and synchronizing the ring buffer to a higher layer during resizing. This guarantees that no writes are occurring while the resize takes place. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-12-11 11:54:27 +08:00
atomic_dec(&buffer->record_disabled);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return size;
free_pages:
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
list_for_each_entry_safe(bpage, tmp, &pages, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
put_online_cpus();
trace: introduce missing mutex_unlock() Impact: fix tracing buffer mutex leak in case of allocation failure This error was spotted by this semantic patch: http://www.emn.fr/x-info/coccinelle/mut.html It looks correct as far as I can tell. Please review. Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-19 02:22:13 +08:00
mutex_unlock(&buffer->mutex);
ring-buffer: Use sync sched protection on ring buffer resizing There was a comment in the ring buffer code that says the calling layers should prevent tracing or reading of the ring buffer while resizing. I have discovered that the tracers do not honor this arrangement. This patch moves the disabling and synchronizing the ring buffer to a higher layer during resizing. This guarantees that no writes are occurring while the resize takes place. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-12-11 11:54:27 +08:00
atomic_dec(&buffer->record_disabled);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return -ENOMEM;
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
/*
* Something went totally wrong, and we are too paranoid
* to even clean up the mess.
*/
out_fail:
put_online_cpus();
mutex_unlock(&buffer->mutex);
ring-buffer: Use sync sched protection on ring buffer resizing There was a comment in the ring buffer code that says the calling layers should prevent tracing or reading of the ring buffer while resizing. I have discovered that the tracers do not honor this arrangement. This patch moves the disabling and synchronizing the ring buffer to a higher layer during resizing. This guarantees that no writes are occurring while the resize takes place. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-12-11 11:54:27 +08:00
atomic_dec(&buffer->record_disabled);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
return -1;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_resize);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
static inline void *
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
{
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
return bpage->data + index;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
}
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
return bpage->page->data + index;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
static inline struct ring_buffer_event *
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
ring-buffer: move page indexes into page headers Remove the global head and tail indexes and move them into the page header. Each page will now keep track of where the last write and read was made. We also rename the head and tail to read and write for better clarification. This patch is needed for future enhancements to move the ring buffer to a lockless solution. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:58 +08:00
return __rb_page_index(cpu_buffer->reader_page,
cpu_buffer->reader_page->read);
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
static inline struct ring_buffer_event *
rb_iter_head_event(struct ring_buffer_iter *iter)
{
ring-buffer: move page indexes into page headers Remove the global head and tail indexes and move them into the page header. Each page will now keep track of where the last write and read was made. We also rename the head and tail to read and write for better clarification. This patch is needed for future enhancements to move the ring buffer to a lockless solution. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:58 +08:00
return __rb_page_index(iter->head_page, iter->head);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
static inline unsigned long rb_page_write(struct buffer_page *bpage)
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
{
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
return local_read(&bpage->write) & RB_WRITE_MASK;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
}
static inline unsigned rb_page_commit(struct buffer_page *bpage)
{
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
return local_read(&bpage->page->commit);
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
}
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
static inline unsigned long rb_page_entries(struct buffer_page *bpage)
{
return local_read(&bpage->entries) & RB_WRITE_MASK;
}
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
/* Size is determined by what has been commited */
static inline unsigned rb_page_size(struct buffer_page *bpage)
{
return rb_page_commit(bpage);
}
static inline unsigned
rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
{
return rb_page_commit(cpu_buffer->commit_page);
}
static inline unsigned
rb_event_index(struct ring_buffer_event *event)
{
unsigned long addr = (unsigned long)event;
ring-buffer: use BUF_PAGE_HDR_SIZE in calculating index The index of the event is found by masking PAGE_MASK to it and subtracting the header size. Currently the header size is calculate by PAGE_SIZE - BUF_PAGE_SIZE, when we already have a macro BUF_PAGE_HDR_SIZE to define it. If we want to change BUF_PAGE_SIZE to something less than filling the rest of the page (this is done for debugging), then we break the algorithm to find the index. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-11 21:29:58 +08:00
return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
}
ring-buffer: small optimizations Doing some small changes in the fast path of the ring buffer recording saves over 3% in the ring-buffer-benchmark test. [ Impact: a little faster ring buffer recording ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 04:08:00 +08:00
static inline int
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
{
unsigned long addr = (unsigned long)event;
unsigned long index;
index = rb_event_index(event);
addr &= PAGE_MASK;
return cpu_buffer->commit_page->page == (void *)addr &&
rb_commit_index(cpu_buffer) == index;
}
kernel/trace/ring_buffer.c: reduce inlining text data bss dec hex filename before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o Also: free_page(0) is legal. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
static void
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
unsigned long max_count;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
/*
* We only race with interrupts and NMIs on this CPU.
* If we own the commit event, then we can commit
* all others that interrupted us, since the interruptions
* are in stack format (they finish before they come
* back to us). This allows us to do a simple loop to
* assign the commit to the tail.
*/
ring-buffer: fix dangling commit race Impact: fix stuck trace-buffers If an interrupt comes in during the rb_set_commit_to_write and pushes the tail page forward just at the right time, the commit updates will miss the adding of the interrupt data. This will cause the commit pointer to cease from moving forward. Thanks to Jiaying Zhang for finding this race. Reported-by: Jiaying Zhang <jiayingz@google.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: <stable@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-24 00:32:24 +08:00
again:
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
max_count = cpu_buffer->buffer->pages * 100;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
if (RB_WARN_ON(cpu_buffer, !(--max_count)))
return;
if (RB_WARN_ON(cpu_buffer,
rb_is_reader_page(cpu_buffer->tail_page)))
return;
local_set(&cpu_buffer->commit_page->page->commit,
rb_page_write(cpu_buffer->commit_page));
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
cpu_buffer->write_stamp =
cpu_buffer->commit_page->page->time_stamp;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
/* add barrier to keep gcc from optimizing too much */
barrier();
}
while (rb_commit_index(cpu_buffer) !=
rb_page_write(cpu_buffer->commit_page)) {
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
local_set(&cpu_buffer->commit_page->page->commit,
rb_page_write(cpu_buffer->commit_page));
RB_WARN_ON(cpu_buffer,
local_read(&cpu_buffer->commit_page->page->commit) &
~RB_WRITE_MASK);
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
barrier();
}
ring-buffer: fix dangling commit race Impact: fix stuck trace-buffers If an interrupt comes in during the rb_set_commit_to_write and pushes the tail page forward just at the right time, the commit updates will miss the adding of the interrupt data. This will cause the commit pointer to cease from moving forward. Thanks to Jiaying Zhang for finding this race. Reported-by: Jiaying Zhang <jiayingz@google.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: <stable@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-24 00:32:24 +08:00
/* again, keep gcc from optimizing */
barrier();
/*
* If an interrupt came in just after the first while loop
* and pushed the tail page forward, we will be left with
* a dangling commit that will never go forward.
*/
if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
goto again;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
ring-buffer: move page indexes into page headers Remove the global head and tail indexes and move them into the page header. Each page will now keep track of where the last write and read was made. We also rename the head and tail to read and write for better clarification. This patch is needed for future enhancements to move the ring buffer to a lockless solution. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:58 +08:00
cpu_buffer->reader_page->read = 0;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
}
kernel/trace/ring_buffer.c: reduce inlining text data bss dec hex filename before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o Also: free_page(0) is legal. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
static void rb_inc_iter(struct ring_buffer_iter *iter)
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
/*
* The iterator could be on the reader page (it starts there).
* But the head could have moved, since the reader was
* found. Check for this case and assign the iterator
* to the head page instead of next.
*/
if (iter->head_page == cpu_buffer->reader_page)
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
iter->head_page = rb_set_head_page(cpu_buffer);
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
else
rb_inc_page(cpu_buffer, &iter->head_page);
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
iter->read_stamp = iter->head_page->page->time_stamp;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
iter->head = 0;
}
/**
* ring_buffer_update_event - update event type and data
* @event: the even to update
* @type: the type of event
* @length: the size of the event field in the ring buffer
*
* Update the type and data fields of the event. The length
* is the actual size that is written to the ring buffer,
* and with this, we can determine what to place into the
* data field.
*/
kernel/trace/ring_buffer.c: reduce inlining text data bss dec hex filename before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o Also: free_page(0) is legal. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
static void
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
rb_update_event(struct ring_buffer_event *event,
unsigned type, unsigned length)
{
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
event->type_len = type;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
switch (type) {
case RINGBUF_TYPE_PADDING:
case RINGBUF_TYPE_TIME_EXTEND:
case RINGBUF_TYPE_TIME_STAMP:
break;
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
case 0:
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
length -= RB_EVNT_HDR_SIZE;
ring-buffer: Do 8 byte alignment for 64 bit that can not handle 4 byte align The ring buffer uses 4 byte alignment while recording events into the buffer, even on 64bit machines. This saves space when there are lots of events being recorded at 4 byte boundaries. The ring buffer has a zero copy method to write into the buffer, with the reserving of space and then committing it. This may cause problems when writing an 8 byte word into a 4 byte alignment (not 8). For x86 and PPC this is not an issue, but on some architectures this would cause an out-of-alignment exception. This patch uses CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to determine if it is OK to use 4 byte alignments on 64 bit machines. If it is not, it forces the ring buffer event header to be 8 bytes and not 4, and will align the length of the data to be 8 byte aligned. This keeps the data payload at 8 byte alignments and will allow these machines to run without issue. The trick to this is that the header can be either 4 bytes or 8 bytes depending on the length of the data payload. The 4 byte header has a length field that supports up to 112 bytes. If the length of the data is more than 112, the length field is set to zero, and the actual length is stored in the next 4 bytes after the header. When CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is not set, the code forces zero in the 4 byte header forcing the length to be stored in the 4 byte array, even with a small data load. It also forces the length of the data load to be 8 byte aligned. The combination of these two guarantee that the data is always at 8 byte alignment. Tested-by: Frederic Weisbecker <fweisbec@gmail.com> (on sparc64) Reported-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-19 05:54:19 +08:00
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
event->array[0] = length;
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
else
event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
break;
default:
BUG();
}
}
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/*
* rb_handle_head_page - writer hit the head page
*
* Returns: +1 to retry page
* 0 to continue
* -1 on error
*/
static int
rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *tail_page,
struct buffer_page *next_page)
{
struct buffer_page *new_head;
int entries;
int type;
int ret;
entries = rb_page_entries(next_page);
/*
* The hard part is here. We need to move the head
* forward, and protect against both readers on
* other CPUs and writers coming in via interrupts.
*/
type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
RB_PAGE_HEAD);
/*
* type can be one of four:
* NORMAL - an interrupt already moved it for us
* HEAD - we are the first to get here.
* UPDATE - we are the interrupt interrupting
* a current move.
* MOVED - a reader on another CPU moved the next
* pointer to its reader page. Give up
* and try again.
*/
switch (type) {
case RB_PAGE_HEAD:
/*
* We changed the head to UPDATE, thus
* it is our responsibility to update
* the counters.
*/
local_add(entries, &cpu_buffer->overrun);
/*
* The entries will be zeroed out when we move the
* tail page.
*/
/* still more to do */
break;
case RB_PAGE_UPDATE:
/*
* This is an interrupt that interrupt the
* previous update. Still more to do.
*/
break;
case RB_PAGE_NORMAL:
/*
* An interrupt came in before the update
* and processed this for us.
* Nothing left to do.
*/
return 1;
case RB_PAGE_MOVED:
/*
* The reader is on another CPU and just did
* a swap with our next_page.
* Try again.
*/
return 1;
default:
RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
return -1;
}
/*
* Now that we are here, the old head pointer is
* set to UPDATE. This will keep the reader from
* swapping the head page with the reader page.
* The reader (on another CPU) will spin till
* we are finished.
*
* We just need to protect against interrupts
* doing the job. We will set the next pointer
* to HEAD. After that, we set the old pointer
* to NORMAL, but only if it was HEAD before.
* otherwise we are an interrupt, and only
* want the outer most commit to reset it.
*/
new_head = next_page;
rb_inc_page(cpu_buffer, &new_head);
ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
RB_PAGE_NORMAL);
/*
* Valid returns are:
* HEAD - an interrupt came in and already set it.
* NORMAL - One of two things:
* 1) We really set it.
* 2) A bunch of interrupts came in and moved
* the page forward again.
*/
switch (ret) {
case RB_PAGE_HEAD:
case RB_PAGE_NORMAL:
/* OK */
break;
default:
RB_WARN_ON(cpu_buffer, 1);
return -1;
}
/*
* It is possible that an interrupt came in,
* set the head up, then more interrupts came in
* and moved it again. When we get back here,
* the page would have been set to NORMAL but we
* just set it back to HEAD.
*
* How do you detect this? Well, if that happened
* the tail page would have moved.
*/
if (ret == RB_PAGE_NORMAL) {
/*
* If the tail had moved passed next, then we need
* to reset the pointer.
*/
if (cpu_buffer->tail_page != tail_page &&
cpu_buffer->tail_page != next_page)
rb_head_page_set_normal(cpu_buffer, new_head,
next_page,
RB_PAGE_HEAD);
}
/*
* If this was the outer most commit (the one that
* changed the original pointer from HEAD to UPDATE),
* then it is up to us to reset it to NORMAL.
*/
if (type == RB_PAGE_HEAD) {
ret = rb_head_page_set_normal(cpu_buffer, next_page,
tail_page,
RB_PAGE_UPDATE);
if (RB_WARN_ON(cpu_buffer,
ret != RB_PAGE_UPDATE))
return -1;
}
return 0;
}
kernel/trace/ring_buffer.c: reduce inlining text data bss dec hex filename before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o Also: free_page(0) is legal. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
static unsigned rb_calculate_event_length(unsigned length)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
struct ring_buffer_event event; /* Used only for sizeof array */
/* zero length can cause confusions */
if (!length)
length = 1;
ring-buffer: Do 8 byte alignment for 64 bit that can not handle 4 byte align The ring buffer uses 4 byte alignment while recording events into the buffer, even on 64bit machines. This saves space when there are lots of events being recorded at 4 byte boundaries. The ring buffer has a zero copy method to write into the buffer, with the reserving of space and then committing it. This may cause problems when writing an 8 byte word into a 4 byte alignment (not 8). For x86 and PPC this is not an issue, but on some architectures this would cause an out-of-alignment exception. This patch uses CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to determine if it is OK to use 4 byte alignments on 64 bit machines. If it is not, it forces the ring buffer event header to be 8 bytes and not 4, and will align the length of the data to be 8 byte aligned. This keeps the data payload at 8 byte alignments and will allow these machines to run without issue. The trick to this is that the header can be either 4 bytes or 8 bytes depending on the length of the data payload. The 4 byte header has a length field that supports up to 112 bytes. If the length of the data is more than 112, the length field is set to zero, and the actual length is stored in the next 4 bytes after the header. When CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is not set, the code forces zero in the 4 byte header forcing the length to be stored in the 4 byte array, even with a small data load. It also forces the length of the data load to be 8 byte aligned. The combination of these two guarantee that the data is always at 8 byte alignment. Tested-by: Frederic Weisbecker <fweisbec@gmail.com> (on sparc64) Reported-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-19 05:54:19 +08:00
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
length += sizeof(event.array[0]);
length += RB_EVNT_HDR_SIZE;
ring-buffer: Do 8 byte alignment for 64 bit that can not handle 4 byte align The ring buffer uses 4 byte alignment while recording events into the buffer, even on 64bit machines. This saves space when there are lots of events being recorded at 4 byte boundaries. The ring buffer has a zero copy method to write into the buffer, with the reserving of space and then committing it. This may cause problems when writing an 8 byte word into a 4 byte alignment (not 8). For x86 and PPC this is not an issue, but on some architectures this would cause an out-of-alignment exception. This patch uses CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to determine if it is OK to use 4 byte alignments on 64 bit machines. If it is not, it forces the ring buffer event header to be 8 bytes and not 4, and will align the length of the data to be 8 byte aligned. This keeps the data payload at 8 byte alignments and will allow these machines to run without issue. The trick to this is that the header can be either 4 bytes or 8 bytes depending on the length of the data payload. The 4 byte header has a length field that supports up to 112 bytes. If the length of the data is more than 112, the length field is set to zero, and the actual length is stored in the next 4 bytes after the header. When CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is not set, the code forces zero in the 4 byte header forcing the length to be stored in the 4 byte array, even with a small data load. It also forces the length of the data load to be 8 byte aligned. The combination of these two guarantee that the data is always at 8 byte alignment. Tested-by: Frederic Weisbecker <fweisbec@gmail.com> (on sparc64) Reported-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-19 05:54:19 +08:00
length = ALIGN(length, RB_ARCH_ALIGNMENT);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return length;
}
ring-buffer: prevent adding write in discarded area This a very tight race where an interrupt could come in and not have enough data to put into the end of a buffer page, and that it would fail to write and need to go to the next page. But if this happened when another writer was about to reserver their data, and that writer has smaller data to reserve, then it could succeed even though the interrupt moved the tail page. To pervent that, if we fail to store data, and by subtracting the amount we reserved we still have room for smaller data, we need to fill that space with "discarded" data. [ Impact: prevent race were buffer data may be lost ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-11 23:12:00 +08:00
static inline void
rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *tail_page,
unsigned long tail, unsigned long length)
{
struct ring_buffer_event *event;
/*
* Only the event that crossed the page boundary
* must fill the old tail_page with padding.
*/
if (tail >= BUF_PAGE_SIZE) {
ring-buffer: Reset "real_end" when page is filled The code to store the "lost events" requires knowing the real end of the page. Since the 'commit' includes the padding at the end of a page a "real_end" variable was used to keep track of the end not including the padding. If events were lost, the reader can place the count of events in the padded area if there is enough room. The bug this patch fixes is that when we fill the page we do not reset the real_end variable, and if the writer had wrapped a few times, the real_end would be incorrect. This patch simply resets the real_end if the page was filled. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-05-21 23:55:21 +08:00
/*
* If the page was filled, then we still need
* to update the real_end. Reset it to zero
* and the reader will ignore it.
*/
if (tail == BUF_PAGE_SIZE)
tail_page->real_end = 0;
ring-buffer: prevent adding write in discarded area This a very tight race where an interrupt could come in and not have enough data to put into the end of a buffer page, and that it would fail to write and need to go to the next page. But if this happened when another writer was about to reserver their data, and that writer has smaller data to reserve, then it could succeed even though the interrupt moved the tail page. To pervent that, if we fail to store data, and by subtracting the amount we reserved we still have room for smaller data, we need to fill that space with "discarded" data. [ Impact: prevent race were buffer data may be lost ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-11 23:12:00 +08:00
local_sub(length, &tail_page->write);
return;
}
event = __rb_page_index(tail_page, tail);
Merge branch 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (24 commits) tracing/urgent: warn in case of ftrace_start_up inbalance tracing/urgent: fix unbalanced ftrace_start_up function-graph: add stack frame test function-graph: disable when both x86_32 and optimize for size are configured ring-buffer: have benchmark test print to trace buffer ring-buffer: do not grab locks in nmi ring-buffer: add locks around rb_per_cpu_empty ring-buffer: check for less than two in size allocation ring-buffer: remove useless compile check for buffer_page size ring-buffer: remove useless warn on check ring-buffer: use BUF_PAGE_HDR_SIZE in calculating index tracing: update sample event documentation tracing/filters: fix race between filter setting and module unload tracing/filters: free filter_string in destroy_preds() ring-buffer: use commit counters for commit pointer accounting ring-buffer: remove unused variable ring-buffer: have benchmark test handle discarded events ring-buffer: prevent adding write in discarded area tracing/filters: strloc should be unsigned short tracing/filters: operand can be negative ... Fix up kmemcheck-induced conflict in kernel/trace/ring_buffer.c manually
2009-06-21 01:56:46 +08:00
kmemcheck_annotate_bitfield(event, bitfield);
ring-buffer: prevent adding write in discarded area This a very tight race where an interrupt could come in and not have enough data to put into the end of a buffer page, and that it would fail to write and need to go to the next page. But if this happened when another writer was about to reserver their data, and that writer has smaller data to reserve, then it could succeed even though the interrupt moved the tail page. To pervent that, if we fail to store data, and by subtracting the amount we reserved we still have room for smaller data, we need to fill that space with "discarded" data. [ Impact: prevent race were buffer data may be lost ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-11 23:12:00 +08:00
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
/*
* Save the original length to the meta data.
* This will be used by the reader to add lost event
* counter.
*/
tail_page->real_end = tail;
ring-buffer: prevent adding write in discarded area This a very tight race where an interrupt could come in and not have enough data to put into the end of a buffer page, and that it would fail to write and need to go to the next page. But if this happened when another writer was about to reserver their data, and that writer has smaller data to reserve, then it could succeed even though the interrupt moved the tail page. To pervent that, if we fail to store data, and by subtracting the amount we reserved we still have room for smaller data, we need to fill that space with "discarded" data. [ Impact: prevent race were buffer data may be lost ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-11 23:12:00 +08:00
/*
* If this event is bigger than the minimum size, then
* we need to be careful that we don't subtract the
* write counter enough to allow another writer to slip
* in on this page.
* We put in a discarded commit instead, to make sure
* that this space is not used again.
*
* If we are less than the minimum size, we don't need to
* worry about it.
*/
if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
/* No room for any events */
/* Mark the rest of the page with padding */
rb_event_set_padding(event);
/* Set the write back to the previous setting */
local_sub(length, &tail_page->write);
return;
}
/* Put in a discarded event */
event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
event->type_len = RINGBUF_TYPE_PADDING;
/* time delta must be non zero */
event->time_delta = 1;
/* Set write to end of buffer */
length = (tail + length) - BUF_PAGE_SIZE;
local_sub(length, &tail_page->write);
}
ring-buffer: make moving the tail page a separate function Ingo Molnar thought the code would be cleaner if we used a function call instead of a goto for moving the tail page. After implementing this, it seems that gcc still inlines the result and the output is pretty much the same. Since this is considered a cleaner approach, might as well implement it. [ Impact: code clean up ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-07 03:30:07 +08:00
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
static struct ring_buffer_event *
ring-buffer: make moving the tail page a separate function Ingo Molnar thought the code would be cleaner if we used a function call instead of a goto for moving the tail page. After implementing this, it seems that gcc still inlines the result and the output is pretty much the same. Since this is considered a cleaner approach, might as well implement it. [ Impact: code clean up ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-07 03:30:07 +08:00
rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
unsigned long length, unsigned long tail,
struct buffer_page *tail_page, u64 *ts)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
ring-buffer: Move access to commit_page up into function used With the change of the way we process commits. Where a commit only happens at the outer most level, and that we don't need to worry about a commit ending after the rb_start_commit() has been called, the code use to grab the commit page before the tail page to prevent a possible race. But this race no longer exists with the rb_start_commit() rb_end_commit() interface. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-11-17 21:43:01 +08:00
struct buffer_page *commit_page = cpu_buffer->commit_page;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
struct ring_buffer *buffer = cpu_buffer->buffer;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
struct buffer_page *next_page;
int ret;
ring-buffer: move big if statement down In the hot path of the ring buffer "__rb_reserve_next" there's a big if statement that does not even return back to the work flow. code; if (cross to next page) { [ lots of code ] return; } more code; The condition is even the unlikely path, although we do not denote it with an unlikely because gcc is fine with it. The condition is true when the write crosses a page boundary, and we need to start at a new page. Having this if statement makes it hard to read, but calling another function to do the work is also not appropriate, because we are using a lot of variables that were set before the if statement, and we do not want to send them as parameters. This patch changes it to a goto: code; if (cross to next page) goto next_page; more code; return; next_page: [ lots of code] This makes the code easier to understand, and a bit more obvious. The output from gcc is practically identical. For some reason, gcc decided to use different registers when I switched it to a goto. But other than that, the logic is the same. [ Impact: easier to read code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-06 09:16:11 +08:00
next_page = tail_page;
rb_inc_page(cpu_buffer, &next_page);
/*
* If for some reason, we had an interrupt storm that made
* it all the way around the buffer, bail, and warn
* about it.
*/
if (unlikely(next_page == commit_page)) {
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
local_inc(&cpu_buffer->commit_overrun);
ring-buffer: move big if statement down In the hot path of the ring buffer "__rb_reserve_next" there's a big if statement that does not even return back to the work flow. code; if (cross to next page) { [ lots of code ] return; } more code; The condition is even the unlikely path, although we do not denote it with an unlikely because gcc is fine with it. The condition is true when the write crosses a page boundary, and we need to start at a new page. Having this if statement makes it hard to read, but calling another function to do the work is also not appropriate, because we are using a lot of variables that were set before the if statement, and we do not want to send them as parameters. This patch changes it to a goto: code; if (cross to next page) goto next_page; more code; return; next_page: [ lots of code] This makes the code easier to understand, and a bit more obvious. The output from gcc is practically identical. For some reason, gcc decided to use different registers when I switched it to a goto. But other than that, the logic is the same. [ Impact: easier to read code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-06 09:16:11 +08:00
goto out_reset;
}
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/*
* This is where the fun begins!
*
* We are fighting against races between a reader that
* could be on another CPU trying to swap its reader
* page with the buffer head.
*
* We are also fighting against interrupts coming in and
* moving the head or tail on us as well.
*
* If the next page is the head page then we have filled
* the buffer, unless the commit page is still on the
* reader page.
*/
if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
ring-buffer: move big if statement down In the hot path of the ring buffer "__rb_reserve_next" there's a big if statement that does not even return back to the work flow. code; if (cross to next page) { [ lots of code ] return; } more code; The condition is even the unlikely path, although we do not denote it with an unlikely because gcc is fine with it. The condition is true when the write crosses a page boundary, and we need to start at a new page. Having this if statement makes it hard to read, but calling another function to do the work is also not appropriate, because we are using a lot of variables that were set before the if statement, and we do not want to send them as parameters. This patch changes it to a goto: code; if (cross to next page) goto next_page; more code; return; next_page: [ lots of code] This makes the code easier to understand, and a bit more obvious. The output from gcc is practically identical. For some reason, gcc decided to use different registers when I switched it to a goto. But other than that, the logic is the same. [ Impact: easier to read code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-06 09:16:11 +08:00
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/*
* If the commit is not on the reader page, then
* move the header page.
*/
if (!rb_is_reader_page(cpu_buffer->commit_page)) {
/*
* If we are not in overwrite mode,
* this is easy, just stop here.
*/
if (!(buffer->flags & RB_FL_OVERWRITE))
goto out_reset;
ret = rb_handle_head_page(cpu_buffer,
tail_page,
next_page);
if (ret < 0)
goto out_reset;
if (ret)
goto out_again;
} else {
/*
* We need to be careful here too. The
* commit page could still be on the reader
* page. We could have a small buffer, and
* have filled up the buffer with events
* from interrupts and such, and wrapped.
*
* Note, if the tail page is also the on the
* reader_page, we let it move out.
*/
if (unlikely((cpu_buffer->commit_page !=
cpu_buffer->tail_page) &&
(cpu_buffer->commit_page ==
cpu_buffer->reader_page))) {
local_inc(&cpu_buffer->commit_overrun);
goto out_reset;
}
ring-buffer: move big if statement down In the hot path of the ring buffer "__rb_reserve_next" there's a big if statement that does not even return back to the work flow. code; if (cross to next page) { [ lots of code ] return; } more code; The condition is even the unlikely path, although we do not denote it with an unlikely because gcc is fine with it. The condition is true when the write crosses a page boundary, and we need to start at a new page. Having this if statement makes it hard to read, but calling another function to do the work is also not appropriate, because we are using a lot of variables that were set before the if statement, and we do not want to send them as parameters. This patch changes it to a goto: code; if (cross to next page) goto next_page; more code; return; next_page: [ lots of code] This makes the code easier to understand, and a bit more obvious. The output from gcc is practically identical. For some reason, gcc decided to use different registers when I switched it to a goto. But other than that, the logic is the same. [ Impact: easier to read code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-06 09:16:11 +08:00
}
}
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
ret = rb_tail_page_update(cpu_buffer, tail_page, next_page);
if (ret) {
/*
* Nested commits always have zero deltas, so
* just reread the time stamp
*/
tracing: Remove cpu arg from the rb_time_stamp() function The cpu argument is not used inside the rb_time_stamp() function. Plus fix a typo. Signed-off-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20091023233647.118547500@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-24 07:36:19 +08:00
*ts = rb_time_stamp(buffer);
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
next_page->page->time_stamp = *ts;
ring-buffer: move big if statement down In the hot path of the ring buffer "__rb_reserve_next" there's a big if statement that does not even return back to the work flow. code; if (cross to next page) { [ lots of code ] return; } more code; The condition is even the unlikely path, although we do not denote it with an unlikely because gcc is fine with it. The condition is true when the write crosses a page boundary, and we need to start at a new page. Having this if statement makes it hard to read, but calling another function to do the work is also not appropriate, because we are using a lot of variables that were set before the if statement, and we do not want to send them as parameters. This patch changes it to a goto: code; if (cross to next page) goto next_page; more code; return; next_page: [ lots of code] This makes the code easier to understand, and a bit more obvious. The output from gcc is practically identical. For some reason, gcc decided to use different registers when I switched it to a goto. But other than that, the logic is the same. [ Impact: easier to read code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-06 09:16:11 +08:00
}
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
out_again:
ring-buffer: move big if statement down In the hot path of the ring buffer "__rb_reserve_next" there's a big if statement that does not even return back to the work flow. code; if (cross to next page) { [ lots of code ] return; } more code; The condition is even the unlikely path, although we do not denote it with an unlikely because gcc is fine with it. The condition is true when the write crosses a page boundary, and we need to start at a new page. Having this if statement makes it hard to read, but calling another function to do the work is also not appropriate, because we are using a lot of variables that were set before the if statement, and we do not want to send them as parameters. This patch changes it to a goto: code; if (cross to next page) goto next_page; more code; return; next_page: [ lots of code] This makes the code easier to understand, and a bit more obvious. The output from gcc is practically identical. For some reason, gcc decided to use different registers when I switched it to a goto. But other than that, the logic is the same. [ Impact: easier to read code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-06 09:16:11 +08:00
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_reset_tail(cpu_buffer, tail_page, tail, length);
ring-buffer: move big if statement down In the hot path of the ring buffer "__rb_reserve_next" there's a big if statement that does not even return back to the work flow. code; if (cross to next page) { [ lots of code ] return; } more code; The condition is even the unlikely path, although we do not denote it with an unlikely because gcc is fine with it. The condition is true when the write crosses a page boundary, and we need to start at a new page. Having this if statement makes it hard to read, but calling another function to do the work is also not appropriate, because we are using a lot of variables that were set before the if statement, and we do not want to send them as parameters. This patch changes it to a goto: code; if (cross to next page) goto next_page; more code; return; next_page: [ lots of code] This makes the code easier to understand, and a bit more obvious. The output from gcc is practically identical. For some reason, gcc decided to use different registers when I switched it to a goto. But other than that, the logic is the same. [ Impact: easier to read code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-06 09:16:11 +08:00
/* fail and let the caller try again */
return ERR_PTR(-EAGAIN);
ring-buffer: rename label out_unlock to out_reset Impact: clean up While reviewing the ring buffer code, I thougth I saw a bug with if (!__raw_spin_trylock(&cpu_buffer->lock)) goto out_unlock; But I forgot that we use a variable "lock_taken" that is set if the spinlock is taken, and only unlock it if that variable is set. To avoid further confusion from other reviewers, this patch renames the label out_unlock with out_reset, which is the more appropriate name. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-13 02:19:48 +08:00
out_reset:
ring_buffer: reset write when reserve buffer fail Impact: reset struct buffer_page.write when interrupt storm if struct buffer_page.write is not reset, any succedent committing will corrupted ring_buffer: static inline void rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) { ...... cpu_buffer->commit_page->commit = cpu_buffer->commit_page->write; ...... } when "if (RB_WARN_ON(cpu_buffer, next_page == reader_page))", ring_buffer is disabled, but some reserved buffers may haven't been committed. we need reset struct buffer_page.write. when "if (unlikely(next_page == cpu_buffer->commit_page))", ring_buffer is still available, we should not corrupt it. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-12 11:06:18 +08:00
/* reset write */
ring-buffer: prevent adding write in discarded area This a very tight race where an interrupt could come in and not have enough data to put into the end of a buffer page, and that it would fail to write and need to go to the next page. But if this happened when another writer was about to reserver their data, and that writer has smaller data to reserve, then it could succeed even though the interrupt moved the tail page. To pervent that, if we fail to store data, and by subtracting the amount we reserved we still have room for smaller data, we need to fill that space with "discarded" data. [ Impact: prevent race were buffer data may be lost ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-11 23:12:00 +08:00
rb_reset_tail(cpu_buffer, tail_page, tail, length);
ring_buffer: reset write when reserve buffer fail Impact: reset struct buffer_page.write when interrupt storm if struct buffer_page.write is not reset, any succedent committing will corrupted ring_buffer: static inline void rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) { ...... cpu_buffer->commit_page->commit = cpu_buffer->commit_page->write; ...... } when "if (RB_WARN_ON(cpu_buffer, next_page == reader_page))", ring_buffer is disabled, but some reserved buffers may haven't been committed. we need reset struct buffer_page.write. when "if (unlikely(next_page == cpu_buffer->commit_page))", ring_buffer is still available, we should not corrupt it. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-12 11:06:18 +08:00
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
return NULL;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: make moving the tail page a separate function Ingo Molnar thought the code would be cleaner if we used a function call instead of a goto for moving the tail page. After implementing this, it seems that gcc still inlines the result and the output is pretty much the same. Since this is considered a cleaner approach, might as well implement it. [ Impact: code clean up ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-07 03:30:07 +08:00
static struct ring_buffer_event *
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
unsigned type, unsigned long length, u64 *ts)
{
ring-buffer: Move access to commit_page up into function used With the change of the way we process commits. Where a commit only happens at the outer most level, and that we don't need to worry about a commit ending after the rb_start_commit() has been called, the code use to grab the commit page before the tail page to prevent a possible race. But this race no longer exists with the rb_start_commit() rb_end_commit() interface. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-11-17 21:43:01 +08:00
struct buffer_page *tail_page;
ring-buffer: make moving the tail page a separate function Ingo Molnar thought the code would be cleaner if we used a function call instead of a goto for moving the tail page. After implementing this, it seems that gcc still inlines the result and the output is pretty much the same. Since this is considered a cleaner approach, might as well implement it. [ Impact: code clean up ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-07 03:30:07 +08:00
struct ring_buffer_event *event;
unsigned long tail, write;
tail_page = cpu_buffer->tail_page;
write = local_add_return(length, &tail_page->write);
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/* set write to only the index of the write */
write &= RB_WRITE_MASK;
ring-buffer: make moving the tail page a separate function Ingo Molnar thought the code would be cleaner if we used a function call instead of a goto for moving the tail page. After implementing this, it seems that gcc still inlines the result and the output is pretty much the same. Since this is considered a cleaner approach, might as well implement it. [ Impact: code clean up ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-07 03:30:07 +08:00
tail = write - length;
/* See if we shot pass the end of this buffer page */
if (write > BUF_PAGE_SIZE)
return rb_move_tail(cpu_buffer, length, tail,
ring-buffer: Move access to commit_page up into function used With the change of the way we process commits. Where a commit only happens at the outer most level, and that we don't need to worry about a commit ending after the rb_start_commit() has been called, the code use to grab the commit page before the tail page to prevent a possible race. But this race no longer exists with the rb_start_commit() rb_end_commit() interface. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-11-17 21:43:01 +08:00
tail_page, ts);
ring-buffer: make moving the tail page a separate function Ingo Molnar thought the code would be cleaner if we used a function call instead of a goto for moving the tail page. After implementing this, it seems that gcc still inlines the result and the output is pretty much the same. Since this is considered a cleaner approach, might as well implement it. [ Impact: code clean up ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-07 03:30:07 +08:00
/* We reserved something on the buffer */
event = __rb_page_index(tail_page, tail);
trace: annotate bitfields in struct ring_buffer_event This gets rid of a heap of false-positive warnings from the tracer code due to the use of bitfields. [rebased for mainline inclusion] Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
2009-02-28 15:29:44 +08:00
kmemcheck_annotate_bitfield(event, bitfield);
ring-buffer: make moving the tail page a separate function Ingo Molnar thought the code would be cleaner if we used a function call instead of a goto for moving the tail page. After implementing this, it seems that gcc still inlines the result and the output is pretty much the same. Since this is considered a cleaner approach, might as well implement it. [ Impact: code clean up ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-07 03:30:07 +08:00
rb_update_event(event, type, length);
/* The passed in type is zero for DATA */
if (likely(!type))
local_inc(&tail_page->entries);
/*
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
* If this is the first commit on the page, then update
* its timestamp.
ring-buffer: make moving the tail page a separate function Ingo Molnar thought the code would be cleaner if we used a function call instead of a goto for moving the tail page. After implementing this, it seems that gcc still inlines the result and the output is pretty much the same. Since this is considered a cleaner approach, might as well implement it. [ Impact: code clean up ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-07 03:30:07 +08:00
*/
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
if (!tail)
tail_page->page->time_stamp = *ts;
ring-buffer: make moving the tail page a separate function Ingo Molnar thought the code would be cleaner if we used a function call instead of a goto for moving the tail page. After implementing this, it seems that gcc still inlines the result and the output is pretty much the same. Since this is considered a cleaner approach, might as well implement it. [ Impact: code clean up ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-07 03:30:07 +08:00
return event;
}
ring-buffer: try to discard unneeded timestamps There are times that a race may happen that we add a timestamp in a nested write. This timestamp would just contain a zero delta and serves no purpose. Now that we have a way to discard events, this patch will try to discard the timestamp instead of just wasting the space in the ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 11:00:53 +08:00
static inline int
rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
unsigned long new_index, old_index;
struct buffer_page *bpage;
unsigned long index;
unsigned long addr;
new_index = rb_event_index(event);
old_index = new_index + rb_event_length(event);
addr = (unsigned long)event;
addr &= PAGE_MASK;
bpage = cpu_buffer->tail_page;
if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
unsigned long write_mask =
local_read(&bpage->write) & ~RB_WRITE_MASK;
ring-buffer: try to discard unneeded timestamps There are times that a race may happen that we add a timestamp in a nested write. This timestamp would just contain a zero delta and serves no purpose. Now that we have a way to discard events, this patch will try to discard the timestamp instead of just wasting the space in the ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 11:00:53 +08:00
/*
* This is on the tail page. It is possible that
* a write could come in and move the tail page
* and write to the next page. That is fine
* because we just shorten what is on this page.
*/
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
old_index += write_mask;
new_index += write_mask;
ring-buffer: try to discard unneeded timestamps There are times that a race may happen that we add a timestamp in a nested write. This timestamp would just contain a zero delta and serves no purpose. Now that we have a way to discard events, this patch will try to discard the timestamp instead of just wasting the space in the ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 11:00:53 +08:00
index = local_cmpxchg(&bpage->write, old_index, new_index);
if (index == old_index)
return 1;
}
/* could not discard */
return 0;
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
static int
rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
u64 *ts, u64 *delta)
{
struct ring_buffer_event *event;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
int ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: Wrap open-coded WARN_ONCE Wrap open-coded WARN_ONCE functionality into the equivalent macro. Signed-off-by: Borislav Petkov <bp@alien8.de> LKML-Reference: <20100502060354.GA5281@liondog.tnic> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-05-02 14:03:54 +08:00
WARN_ONCE(*delta > (1ULL << 59),
KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n",
(unsigned long long)*delta,
(unsigned long long)*ts,
(unsigned long long)cpu_buffer->write_stamp);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/*
* The delta is too big, we to add a
* new timestamp.
*/
event = __rb_reserve_next(cpu_buffer,
RINGBUF_TYPE_TIME_EXTEND,
RB_LEN_TIME_EXTEND,
ts);
if (!event)
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
return -EBUSY;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
if (PTR_ERR(event) == -EAGAIN)
return -EAGAIN;
/* Only a commited time event can update the write stamp */
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
if (rb_event_is_commit(cpu_buffer, event)) {
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
/*
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
* If this is the first on the page, then it was
* updated with the page itself. Try to discard it
* and if we can't just make it zero.
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
*/
if (rb_event_index(event)) {
event->time_delta = *delta & TS_MASK;
event->array[0] = *delta >> TS_SHIFT;
} else {
ring-buffer: discard timestamps that are at the start of the buffer Every buffer page in the ring buffer includes its own time stamp. When an event is recorded to the ring buffer with a delta time greater than what can be held in the event header, a time stamp event is created. If the the create timestamp falls over to the next buffer page, it is redundant because the buffer page holds a full time stamp. This patch will try to discard the time stamp when it falls to the start of the next page. This change also fixes a issues with disarding events. If most events are discarded, timestamps will start to creep into the ring buffer. If we do not discard the timestamps then they can fill up the ring buffer over time and waste space. This change will keep time stamps from filling up over another page. If something is recorded in the buffer page, and the rest is filtered, then the time stamps can only fill up to the end of the page. [ Impact: prevent time stamps from filling ring buffer ] Reported-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 21:30:10 +08:00
/* try to discard, since we do not need this */
if (!rb_try_to_discard(cpu_buffer, event)) {
/* nope, just zero it */
event->time_delta = 0;
event->array[0] = 0;
}
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer->write_stamp = *ts;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
/* let the caller know this was the commit */
ret = 1;
} else {
ring-buffer: try to discard unneeded timestamps There are times that a race may happen that we add a timestamp in a nested write. This timestamp would just contain a zero delta and serves no purpose. Now that we have a way to discard events, this patch will try to discard the timestamp instead of just wasting the space in the ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 11:00:53 +08:00
/* Try to discard the event */
if (!rb_try_to_discard(cpu_buffer, event)) {
/* Darn, this is just wasted space */
event->time_delta = 0;
event->array[0] = 0;
}
ring-buffer: fix ret in rb_add_time_stamp The update of ret got mistakenly added to the if statement of rb_try_to_discard. The variable ret should be 1 on commit and zero otherwise. [ Impact: fix compiler warning and real bug ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-06 02:11:30 +08:00
ret = 0;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
*delta = 0;
return ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
{
local_inc(&cpu_buffer->committing);
local_inc(&cpu_buffer->commits);
}
static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
{
unsigned long commits;
if (RB_WARN_ON(cpu_buffer,
!local_read(&cpu_buffer->committing)))
return;
again:
commits = local_read(&cpu_buffer->commits);
/* synchronize with interrupts */
barrier();
if (local_read(&cpu_buffer->committing) == 1)
rb_set_commit_to_write(cpu_buffer);
local_dec(&cpu_buffer->committing);
/* synchronize with interrupts */
barrier();
/*
* Need to account for interrupts coming in between the
* updating of the commit page and the clearing of the
* committing counter.
*/
if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
!local_read(&cpu_buffer->committing)) {
local_inc(&cpu_buffer->committing);
goto again;
}
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
static struct ring_buffer_event *
ring-buffer: check for swapped buffers in start of committing Because the irqsoff tracer can swap an internal CPU buffer, it is possible that a swap happens between the start of the write and before the committing bit is set (the committing bit will disable swapping). This patch adds a check for this and will fail the write if it detects it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-05 02:11:34 +08:00
rb_reserve_next_event(struct ring_buffer *buffer,
struct ring_buffer_per_cpu *cpu_buffer,
ring-buffer: remove type parameter from rb_reserve_next_event The rb_reserve_next_event is only called for the data type (type = 0). There is no reason to pass in the type to the function. Before: text data bss dec hex filename 16554 24 12 16590 40ce kernel/trace/ring_buffer.o After: text data bss dec hex filename 16538 24 12 16574 40be kernel/trace/ring_buffer.o [ Impact: cleaner, smaller and slightly more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 02:08:09 +08:00
unsigned long length)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
struct ring_buffer_event *event;
ring-buffer: move code around to remove some branches This is a bit of micro-optimizations. But since the ring buffer is used in tracing every function call, it is an extreme hot path. Every nanosecond counts. This change shows over 5% improvement in the ring-buffer-benchmark. [ Impact: more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 10:11:05 +08:00
u64 ts, delta = 0;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
int commit = 0;
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
int nr_loops = 0;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
rb_start_commit(cpu_buffer);
ring-buffer: only enable ring_buffer_swap_cpu when needed Since the ability to swap the cpu buffers adds a small overhead to the recording of a trace, we only want to add it when needed. Only the irqsoff and preemptoff tracers use this feature, and both are not recommended for production kernels. This patch disables its use when neither irqsoff nor preemptoff is configured. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-05 02:24:40 +08:00
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
ring-buffer: check for swapped buffers in start of committing Because the irqsoff tracer can swap an internal CPU buffer, it is possible that a swap happens between the start of the write and before the committing bit is set (the committing bit will disable swapping). This patch adds a check for this and will fail the write if it detects it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-05 02:11:34 +08:00
/*
* Due to the ability to swap a cpu buffer from a buffer
* it is possible it was swapped before we committed.
* (committing stops a swap). We check for it here and
* if it happened, we have to fail the write.
*/
barrier();
if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
local_dec(&cpu_buffer->committing);
local_dec(&cpu_buffer->commits);
return NULL;
}
ring-buffer: only enable ring_buffer_swap_cpu when needed Since the ability to swap the cpu buffers adds a small overhead to the recording of a trace, we only want to add it when needed. Only the irqsoff and preemptoff tracers use this feature, and both are not recommended for production kernels. This patch disables its use when neither irqsoff nor preemptoff is configured. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-05 02:24:40 +08:00
#endif
ring-buffer: check for swapped buffers in start of committing Because the irqsoff tracer can swap an internal CPU buffer, it is possible that a swap happens between the start of the write and before the committing bit is set (the committing bit will disable swapping). This patch adds a check for this and will fail the write if it detects it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-05 02:11:34 +08:00
ring-buffer: move calculation of event length The event length is calculated and passed in to rb_reserve_next_event in two different locations. Having rb_reserve_next_event do the calculations directly makes only one location to do the change and causes the calculation to be inlined by gcc. Before: text data bss dec hex filename 16538 24 12 16574 40be kernel/trace/ring_buffer.o After: text data bss dec hex filename 16490 24 12 16526 408e kernel/trace/ring_buffer.o [ Impact: smaller more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 02:42:53 +08:00
length = rb_calculate_event_length(length);
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
again:
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
/*
* We allow for interrupts to reenter here and do a trace.
* If one does, it will cause this original code to loop
* back here. Even with heavy interrupts happening, this
* should only happen a few times in a row. If this happens
* 1000 times in a row, there must be either an interrupt
* storm or we have something buggy.
* Bail!
*/
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
goto out_fail;
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
tracing: Remove cpu arg from the rb_time_stamp() function The cpu argument is not used inside the rb_time_stamp() function. Plus fix a typo. Signed-off-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20091023233647.118547500@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-24 07:36:19 +08:00
ts = rb_time_stamp(cpu_buffer->buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
/*
* Only the first commit can update the timestamp.
* Yes there is a race here. If an interrupt comes in
* just after the conditional and it traces too, then it
* will also check the deltas. More than one timestamp may
* also be made. But only the entry that did the actual
* commit will be something other than zero.
*/
ring-buffer: small optimizations Doing some small changes in the fast path of the ring buffer recording saves over 3% in the ring-buffer-benchmark test. [ Impact: a little faster ring buffer recording ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 04:08:00 +08:00
if (likely(cpu_buffer->tail_page == cpu_buffer->commit_page &&
rb_page_write(cpu_buffer->tail_page) ==
rb_commit_index(cpu_buffer))) {
ring-buffer: move code around to remove some branches This is a bit of micro-optimizations. But since the ring buffer is used in tracing every function call, it is an extreme hot path. Every nanosecond counts. This change shows over 5% improvement in the ring-buffer-benchmark. [ Impact: more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 10:11:05 +08:00
u64 diff;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
ring-buffer: move code around to remove some branches This is a bit of micro-optimizations. But since the ring buffer is used in tracing every function call, it is an extreme hot path. Every nanosecond counts. This change shows over 5% improvement in the ring-buffer-benchmark. [ Impact: more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 10:11:05 +08:00
diff = ts - cpu_buffer->write_stamp;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: move code around to remove some branches This is a bit of micro-optimizations. But since the ring buffer is used in tracing every function call, it is an extreme hot path. Every nanosecond counts. This change shows over 5% improvement in the ring-buffer-benchmark. [ Impact: more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 10:11:05 +08:00
/* make sure this diff is calculated here */
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
barrier();
/* Did the write stamp get updated already? */
if (unlikely(ts < cpu_buffer->write_stamp))
ring-buffer: move code around to remove some branches This is a bit of micro-optimizations. But since the ring buffer is used in tracing every function call, it is an extreme hot path. Every nanosecond counts. This change shows over 5% improvement in the ring-buffer-benchmark. [ Impact: more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 10:11:05 +08:00
goto get_event;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
ring-buffer: move code around to remove some branches This is a bit of micro-optimizations. But since the ring buffer is used in tracing every function call, it is an extreme hot path. Every nanosecond counts. This change shows over 5% improvement in the ring-buffer-benchmark. [ Impact: more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 10:11:05 +08:00
delta = diff;
if (unlikely(test_time_stamp(delta))) {
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
if (commit == -EBUSY)
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
goto out_fail;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
if (commit == -EAGAIN)
goto again;
RB_WARN_ON(cpu_buffer, commit < 0);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: move code around to remove some branches This is a bit of micro-optimizations. But since the ring buffer is used in tracing every function call, it is an extreme hot path. Every nanosecond counts. This change shows over 5% improvement in the ring-buffer-benchmark. [ Impact: more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 10:11:05 +08:00
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: move code around to remove some branches This is a bit of micro-optimizations. But since the ring buffer is used in tracing every function call, it is an extreme hot path. Every nanosecond counts. This change shows over 5% improvement in the ring-buffer-benchmark. [ Impact: more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 10:11:05 +08:00
get_event:
ring-buffer: remove type parameter from rb_reserve_next_event The rb_reserve_next_event is only called for the data type (type = 0). There is no reason to pass in the type to the function. Before: text data bss dec hex filename 16554 24 12 16590 40ce kernel/trace/ring_buffer.o After: text data bss dec hex filename 16538 24 12 16574 40be kernel/trace/ring_buffer.o [ Impact: cleaner, smaller and slightly more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 02:08:09 +08:00
event = __rb_reserve_next(cpu_buffer, 0, length, &ts);
ring-buffer: move code around to remove some branches This is a bit of micro-optimizations. But since the ring buffer is used in tracing every function call, it is an extreme hot path. Every nanosecond counts. This change shows over 5% improvement in the ring-buffer-benchmark. [ Impact: more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 10:11:05 +08:00
if (unlikely(PTR_ERR(event) == -EAGAIN))
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
goto again;
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
if (!event)
goto out_fail;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
if (!rb_event_is_commit(cpu_buffer, event))
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
delta = 0;
event->time_delta = delta;
return event;
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
out_fail:
rb_end_commit(cpu_buffer);
return NULL;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: Make it generally available In hunting down the cause for the hwlat_detector ring buffer spew in my failed -next builds it became obvious that folks are now treating ring_buffer as something that is generic independent of tracing and thus, suitable for public driver consumption. Given that there are only a few minor areas in ring_buffer that have any reliance on CONFIG_TRACING or CONFIG_FUNCTION_TRACER, provide stubs for those and make it generally available. Signed-off-by: Paul Mundt <lethal@linux-sh.org> Cc: Jon Masters <jcm@jonmasters.org> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <20090625053012.GB19944@linux-sh.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-06-25 13:30:12 +08:00
#ifdef CONFIG_TRACING
tracing: use recursive counter over irq level Althought using the irq level (hardirq_count, softirq_count and in_nmi) was nice to detect bad recursion right away, but since the counters are not atomically updated with respect to the interrupts, the function tracer might trigger the test from an interrupt handler before the hardirq_count is updated. This will trigger a false warning. This patch converts the recursive detection to a simple counter. If the depth is greater than 16 then the recursive detection will trigger. 16 is more than enough for any nested interrupts. [ Impact: fix false positive trace recursion detection ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-21 04:16:11 +08:00
#define TRACE_RECURSIVE_DEPTH 16
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
static int trace_recursive_lock(void)
{
tracing: use recursive counter over irq level Althought using the irq level (hardirq_count, softirq_count and in_nmi) was nice to detect bad recursion right away, but since the counters are not atomically updated with respect to the interrupts, the function tracer might trigger the test from an interrupt handler before the hardirq_count is updated. This will trigger a false warning. This patch converts the recursive detection to a simple counter. If the depth is greater than 16 then the recursive detection will trigger. 16 is more than enough for any nested interrupts. [ Impact: fix false positive trace recursion detection ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-21 04:16:11 +08:00
current->trace_recursion++;
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
tracing: use recursive counter over irq level Althought using the irq level (hardirq_count, softirq_count and in_nmi) was nice to detect bad recursion right away, but since the counters are not atomically updated with respect to the interrupts, the function tracer might trigger the test from an interrupt handler before the hardirq_count is updated. This will trigger a false warning. This patch converts the recursive detection to a simple counter. If the depth is greater than 16 then the recursive detection will trigger. 16 is more than enough for any nested interrupts. [ Impact: fix false positive trace recursion detection ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-21 04:16:11 +08:00
if (likely(current->trace_recursion < TRACE_RECURSIVE_DEPTH))
return 0;
tracing/core: Add current context on tracing recursion warning In case of tracing recursion detection, we only get the stacktrace. But the current context may be very useful to debug the issue. This patch adds the softirq/hardirq/nmi context with the warning using lockdep context display to have a familiar output. v2: Use printk_once() v3: drop {hardirq,softirq}_context which depend on lockdep, only keep what is part of current->trace_recursion, sufficient to debug the warning source. [ Impact: print context necessary to debug recursion ] Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2009-04-20 05:38:12 +08:00
tracing: use recursive counter over irq level Althought using the irq level (hardirq_count, softirq_count and in_nmi) was nice to detect bad recursion right away, but since the counters are not atomically updated with respect to the interrupts, the function tracer might trigger the test from an interrupt handler before the hardirq_count is updated. This will trigger a false warning. This patch converts the recursive detection to a simple counter. If the depth is greater than 16 then the recursive detection will trigger. 16 is more than enough for any nested interrupts. [ Impact: fix false positive trace recursion detection ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-21 04:16:11 +08:00
/* Disable all tracing before we do anything else */
tracing_off_permanent();
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
ring-buffer: fix printk output The warning output in trace_recursive_lock uses %d for a long when it should be %ld. [ Impact: fix compile warning ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-28 00:37:49 +08:00
printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:"
tracing: use recursive counter over irq level Althought using the irq level (hardirq_count, softirq_count and in_nmi) was nice to detect bad recursion right away, but since the counters are not atomically updated with respect to the interrupts, the function tracer might trigger the test from an interrupt handler before the hardirq_count is updated. This will trigger a false warning. This patch converts the recursive detection to a simple counter. If the depth is greater than 16 then the recursive detection will trigger. 16 is more than enough for any nested interrupts. [ Impact: fix false positive trace recursion detection ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-21 04:16:11 +08:00
"HC[%lu]:SC[%lu]:NMI[%lu]\n",
current->trace_recursion,
hardirq_count() >> HARDIRQ_SHIFT,
softirq_count() >> SOFTIRQ_SHIFT,
in_nmi());
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
tracing: use recursive counter over irq level Althought using the irq level (hardirq_count, softirq_count and in_nmi) was nice to detect bad recursion right away, but since the counters are not atomically updated with respect to the interrupts, the function tracer might trigger the test from an interrupt handler before the hardirq_count is updated. This will trigger a false warning. This patch converts the recursive detection to a simple counter. If the depth is greater than 16 then the recursive detection will trigger. 16 is more than enough for any nested interrupts. [ Impact: fix false positive trace recursion detection ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-21 04:16:11 +08:00
WARN_ON_ONCE(1);
return -1;
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
}
static void trace_recursive_unlock(void)
{
tracing: use recursive counter over irq level Althought using the irq level (hardirq_count, softirq_count and in_nmi) was nice to detect bad recursion right away, but since the counters are not atomically updated with respect to the interrupts, the function tracer might trigger the test from an interrupt handler before the hardirq_count is updated. This will trigger a false warning. This patch converts the recursive detection to a simple counter. If the depth is greater than 16 then the recursive detection will trigger. 16 is more than enough for any nested interrupts. [ Impact: fix false positive trace recursion detection ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-21 04:16:11 +08:00
WARN_ON_ONCE(!current->trace_recursion);
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
tracing: use recursive counter over irq level Althought using the irq level (hardirq_count, softirq_count and in_nmi) was nice to detect bad recursion right away, but since the counters are not atomically updated with respect to the interrupts, the function tracer might trigger the test from an interrupt handler before the hardirq_count is updated. This will trigger a false warning. This patch converts the recursive detection to a simple counter. If the depth is greater than 16 then the recursive detection will trigger. 16 is more than enough for any nested interrupts. [ Impact: fix false positive trace recursion detection ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-21 04:16:11 +08:00
current->trace_recursion--;
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
}
ring-buffer: Make it generally available In hunting down the cause for the hwlat_detector ring buffer spew in my failed -next builds it became obvious that folks are now treating ring_buffer as something that is generic independent of tracing and thus, suitable for public driver consumption. Given that there are only a few minor areas in ring_buffer that have any reliance on CONFIG_TRACING or CONFIG_FUNCTION_TRACER, provide stubs for those and make it generally available. Signed-off-by: Paul Mundt <lethal@linux-sh.org> Cc: Jon Masters <jcm@jonmasters.org> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <20090625053012.GB19944@linux-sh.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-06-25 13:30:12 +08:00
#else
#define trace_recursive_lock() (0)
#define trace_recursive_unlock() do { } while (0)
#endif
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_lock_reserve - reserve a part of the buffer
* @buffer: the ring buffer to reserve from
* @length: the length of the data to reserve (excluding event header)
*
* Returns a reseverd event on the ring buffer to copy directly to.
* The user of this interface will need to get the body to write into
* and can use the ring_buffer_event_data() interface.
*
* The length is the length of the data needed, not the event length
* which also includes the event header.
*
* Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
* If NULL is returned, then nothing has been allocated or locked.
*/
struct ring_buffer_event *
ring_buffer: remove unused flags parameter Impact: API change, cleanup >From ring_buffer_{lock_reserve,unlock_commit}. $ codiff /tmp/vmlinux.before /tmp/vmlinux.after linux-2.6-tip/kernel/trace/trace.c: trace_vprintk | -14 trace_graph_return | -14 trace_graph_entry | -10 trace_function | -8 __ftrace_trace_stack | -8 ftrace_trace_userstack | -8 tracing_sched_switch_trace | -8 ftrace_trace_special | -12 tracing_sched_wakeup_trace | -8 9 functions changed, 90 bytes removed, diff: -90 linux-2.6-tip/block/blktrace.c: __blk_add_trace | -1 1 function changed, 1 bytes removed, diff: -1 /tmp/vmlinux.after: 10 functions changed, 91 bytes removed, diff: -91 Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Acked-by: Frédéric Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-06 02:12:56 +08:00
ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
tracing: Remove ftrace_preempt_disable/enable The ftrace_preempt_disable/enable functions were to address a recursive race caused by the function tracer. The function tracer traces all functions which makes it easily susceptible to recursion. One area was preempt_enable(). This would call the scheduler and the schedulre would call the function tracer and loop. (So was it thought). The ftrace_preempt_disable/enable was made to protect against recursion inside the scheduler by storing the NEED_RESCHED flag. If it was set before the ftrace_preempt_disable() it would not call schedule on ftrace_preempt_enable(), thinking that if it was set before then it would have already scheduled unless it was already in the scheduler. This worked fine except in the case of SMP, where another task would set the NEED_RESCHED flag for a task on another CPU, and then kick off an IPI to trigger it. This could cause the NEED_RESCHED to be saved at ftrace_preempt_disable() but the IPI to arrive in the the preempt disabled section. The ftrace_preempt_enable() would not call the scheduler because the flag was already set before entring the section. This bug would cause a missed preemption check and cause lower latencies. Investigating further, I found that the recusion caused by the function tracer was not due to schedule(), but due to preempt_schedule(). Now that preempt_schedule is completely annotated with notrace, the recusion no longer is an issue. Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-06-03 21:36:50 +08:00
int cpu;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: add tracing_off_permanent Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-22 01:41:55 +08:00
if (ring_buffer_flags != RB_BUFFERS_ON)
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
return NULL;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
/* If we are tracing schedule, we don't want to recurse */
tracing: Remove ftrace_preempt_disable/enable The ftrace_preempt_disable/enable functions were to address a recursive race caused by the function tracer. The function tracer traces all functions which makes it easily susceptible to recursion. One area was preempt_enable(). This would call the scheduler and the schedulre would call the function tracer and loop. (So was it thought). The ftrace_preempt_disable/enable was made to protect against recursion inside the scheduler by storing the NEED_RESCHED flag. If it was set before the ftrace_preempt_disable() it would not call schedule on ftrace_preempt_enable(), thinking that if it was set before then it would have already scheduled unless it was already in the scheduler. This worked fine except in the case of SMP, where another task would set the NEED_RESCHED flag for a task on another CPU, and then kick off an IPI to trigger it. This could cause the NEED_RESCHED to be saved at ftrace_preempt_disable() but the IPI to arrive in the the preempt disabled section. The ftrace_preempt_enable() would not call the scheduler because the flag was already set before entring the section. This bug would cause a missed preemption check and cause lower latencies. Investigating further, I found that the recusion caused by the function tracer was not due to schedule(), but due to preempt_schedule(). Now that preempt_schedule is completely annotated with notrace, the recusion no longer is an issue. Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-06-03 21:36:50 +08:00
preempt_disable_notrace();
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
ring-buffer: Move disabled check into preempt disable section The ring buffer resizing and resetting relies on a schedule RCU action. The buffers are disabled, a synchronize_sched() is called and then the resize or reset takes place. But this only works if the disabling of the buffers are within the preempt disabled section, otherwise a window exists that the buffers can be written to while a reset or resize takes place. Cc: stable@kernel.org Reported-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <4B949E43.2010906@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-08 14:50:43 +08:00
if (atomic_read(&buffer->record_disabled))
goto out_nocheck;
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
if (trace_recursive_lock())
goto out_nocheck;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu = raw_smp_processor_id();
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer = buffer->buffers[cpu];
if (atomic_read(&cpu_buffer->record_disabled))
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: move calculation of event length The event length is calculated and passed in to rb_reserve_next_event in two different locations. Having rb_reserve_next_event do the calculations directly makes only one location to do the change and causes the calculation to be inlined by gcc. Before: text data bss dec hex filename 16538 24 12 16574 40be kernel/trace/ring_buffer.o After: text data bss dec hex filename 16490 24 12 16526 408e kernel/trace/ring_buffer.o [ Impact: smaller more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 02:42:53 +08:00
if (length > BUF_MAX_DATA_SIZE)
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: check for swapped buffers in start of committing Because the irqsoff tracer can swap an internal CPU buffer, it is possible that a swap happens between the start of the write and before the committing bit is set (the committing bit will disable swapping). This patch adds a check for this and will fail the write if it detects it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-05 02:11:34 +08:00
event = rb_reserve_next_event(buffer, cpu_buffer, length);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
if (!event)
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return event;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
out:
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
trace_recursive_unlock();
out_nocheck:
tracing: Remove ftrace_preempt_disable/enable The ftrace_preempt_disable/enable functions were to address a recursive race caused by the function tracer. The function tracer traces all functions which makes it easily susceptible to recursion. One area was preempt_enable(). This would call the scheduler and the schedulre would call the function tracer and loop. (So was it thought). The ftrace_preempt_disable/enable was made to protect against recursion inside the scheduler by storing the NEED_RESCHED flag. If it was set before the ftrace_preempt_disable() it would not call schedule on ftrace_preempt_enable(), thinking that if it was set before then it would have already scheduled unless it was already in the scheduler. This worked fine except in the case of SMP, where another task would set the NEED_RESCHED flag for a task on another CPU, and then kick off an IPI to trigger it. This could cause the NEED_RESCHED to be saved at ftrace_preempt_disable() but the IPI to arrive in the the preempt disabled section. The ftrace_preempt_enable() would not call the scheduler because the flag was already set before entring the section. This bug would cause a missed preemption check and cause lower latencies. Investigating further, I found that the recusion caused by the function tracer was not due to schedule(), but due to preempt_schedule(). Now that preempt_schedule is completely annotated with notrace, the recusion no longer is an issue. Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-06-03 21:36:50 +08:00
preempt_enable_notrace();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return NULL;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
static void
rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
struct ring_buffer_event *event)
{
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
/*
* The event first in the commit queue updates the
* time stamp.
*/
if (rb_event_is_commit(cpu_buffer, event))
cpu_buffer->write_stamp += event->time_delta;
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
}
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
local_inc(&cpu_buffer->entries);
rb_update_write_stamp(cpu_buffer, event);
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
rb_end_commit(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
/**
* ring_buffer_unlock_commit - commit a reserved
* @buffer: The buffer to commit to
* @event: The event pointer to commit.
*
* This commits the data to the ring buffer, and releases any locks held.
*
* Must be paired with ring_buffer_lock_reserve.
*/
int ring_buffer_unlock_commit(struct ring_buffer *buffer,
ring_buffer: remove unused flags parameter Impact: API change, cleanup >From ring_buffer_{lock_reserve,unlock_commit}. $ codiff /tmp/vmlinux.before /tmp/vmlinux.after linux-2.6-tip/kernel/trace/trace.c: trace_vprintk | -14 trace_graph_return | -14 trace_graph_entry | -10 trace_function | -8 __ftrace_trace_stack | -8 ftrace_trace_userstack | -8 tracing_sched_switch_trace | -8 ftrace_trace_special | -12 tracing_sched_wakeup_trace | -8 9 functions changed, 90 bytes removed, diff: -90 linux-2.6-tip/block/blktrace.c: __blk_add_trace | -1 1 function changed, 1 bytes removed, diff: -1 /tmp/vmlinux.after: 10 functions changed, 91 bytes removed, diff: -91 Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Acked-by: Frédéric Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-06 02:12:56 +08:00
struct ring_buffer_event *event)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu = raw_smp_processor_id();
cpu_buffer = buffer->buffers[cpu];
rb_commit(cpu_buffer, event);
tracing: add same level recursion detection The tracing infrastructure allows for recursion. That is, an interrupt may interrupt the act of tracing an event, and that interrupt may very well perform its own trace. This is a recursive trace, and is fine to do. The problem arises when there is a bug, and the utility doing the trace calls something that recurses back into the tracer. This recursion is not caused by an external event like an interrupt, but by code that is not expected to recurse. The result could be a lockup. This patch adds a bitmask to the task structure that keeps track of the trace recursion. To find the interrupt depth, the following algorithm is used: level = hardirq_count() + softirq_count() + in_nmi; Here, level will be the depth of interrutps and softirqs, and even handles the nmi. Then the corresponding bit is set in the recursion bitmask. If the bit was already set, we know we had a recursion at the same level and we warn about it and fail the writing to the buffer. After the data has been committed to the buffer, we clear the bit. No atomics are needed. The only races are with interrupts and they reset the bitmask before returning anywy. [ Impact: detect same irq level trace recursion ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-17 09:41:52 +08:00
trace_recursive_unlock();
tracing: Remove ftrace_preempt_disable/enable The ftrace_preempt_disable/enable functions were to address a recursive race caused by the function tracer. The function tracer traces all functions which makes it easily susceptible to recursion. One area was preempt_enable(). This would call the scheduler and the schedulre would call the function tracer and loop. (So was it thought). The ftrace_preempt_disable/enable was made to protect against recursion inside the scheduler by storing the NEED_RESCHED flag. If it was set before the ftrace_preempt_disable() it would not call schedule on ftrace_preempt_enable(), thinking that if it was set before then it would have already scheduled unless it was already in the scheduler. This worked fine except in the case of SMP, where another task would set the NEED_RESCHED flag for a task on another CPU, and then kick off an IPI to trigger it. This could cause the NEED_RESCHED to be saved at ftrace_preempt_disable() but the IPI to arrive in the the preempt disabled section. The ftrace_preempt_enable() would not call the scheduler because the flag was already set before entring the section. This bug would cause a missed preemption check and cause lower latencies. Investigating further, I found that the recusion caused by the function tracer was not due to schedule(), but due to preempt_schedule(). Now that preempt_schedule is completely annotated with notrace, the recusion no longer is an issue. Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-06-03 21:36:50 +08:00
preempt_enable_notrace();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return 0;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
tracing/ring-buffer: Add unlock recursion protection on discard The pair of helpers trace_recursive_lock() and trace_recursive_unlock() have been introduced recently to provide generic tracing recursion protection. They are used in a symetric way: - trace_recursive_lock() on buffer reserve - trace_recursive_unlock() on buffer commit However sometimes, we don't commit but discard on entry to the buffer, ie: in case of filter checking. Then we must also unlock the recursion protection on discard time, otherwise the tracing gets definitely deactivated and a warning is raised spuriously, such as: 111.119821] ------------[ cut here ]------------ [ 111.119829] WARNING: at kernel/trace/ring_buffer.c:1498 ring_buffer_lock_reserve+0x1b7/0x1d0() [ 111.119835] Hardware name: AMILO Li 2727 [ 111.119839] Modules linked in: [ 111.119846] Pid: 5731, comm: Xorg Tainted: G W 2.6.30-rc1 #69 [ 111.119851] Call Trace: [ 111.119863] [<ffffffff8025ce68>] warn_slowpath+0xd8/0x130 [ 111.119873] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0 [ 111.119882] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0 [ 111.119891] [<ffffffff802199b0>] ? native_sched_clock+0x20/0x70 [ 111.119899] [<ffffffff80286dee>] ? put_lock_stats+0xe/0x30 [ 111.119906] [<ffffffff80286eb8>] ? lock_release_holdtime+0xa8/0x150 [ 111.119913] [<ffffffff802c8ae7>] ring_buffer_lock_reserve+0x1b7/0x1d0 [ 111.119921] [<ffffffff802cd110>] trace_buffer_lock_reserve+0x30/0x70 [ 111.119930] [<ffffffff802ce000>] trace_current_buffer_lock_reserve+0x20/0x30 [ 111.119939] [<ffffffff802474e8>] ftrace_raw_event_sched_switch+0x58/0x100 [ 111.119948] [<ffffffff808103b7>] __schedule+0x3a7/0x4cd [ 111.119957] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.119964] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.119971] [<ffffffff80810c08>] schedule+0x18/0x40 [ 111.119977] [<ffffffff80810e09>] preempt_schedule+0x39/0x60 [ 111.119985] [<ffffffff80813bd3>] _read_unlock+0x53/0x60 [ 111.119993] [<ffffffff807259d2>] sock_def_readable+0x72/0x80 [ 111.120002] [<ffffffff807ad5ed>] unix_stream_sendmsg+0x24d/0x3d0 [ 111.120011] [<ffffffff807219a3>] sock_aio_write+0x143/0x160 [ 111.120019] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120026] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160 [ 111.120033] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160 [ 111.120042] [<ffffffff8031c283>] do_sync_readv_writev+0xf3/0x140 [ 111.120049] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120057] [<ffffffff80276ff0>] ? autoremove_wake_function+0x0/0x40 [ 111.120067] [<ffffffff8045d489>] ? cap_file_permission+0x9/0x10 [ 111.120074] [<ffffffff8045c1e6>] ? security_file_permission+0x16/0x20 [ 111.120082] [<ffffffff8031cab4>] do_readv_writev+0xd4/0x1f0 [ 111.120089] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120097] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120105] [<ffffffff8031cc18>] vfs_writev+0x48/0x70 [ 111.120111] [<ffffffff8031cd65>] sys_writev+0x55/0xc0 [ 111.120119] [<ffffffff80211e32>] system_call_fastpath+0x16/0x1b [ 111.120125] ---[ end trace 15605f4e98d5ccb5 ]--- [ Impact: fix spurious warning triggering tracing shutdown ] Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2009-04-20 05:39:33 +08:00
static inline void rb_event_discard(struct ring_buffer_event *event)
{
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
/* array[0] holds the actual length for the discarded event */
event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
event->type_len = RINGBUF_TYPE_PADDING;
tracing/ring-buffer: Add unlock recursion protection on discard The pair of helpers trace_recursive_lock() and trace_recursive_unlock() have been introduced recently to provide generic tracing recursion protection. They are used in a symetric way: - trace_recursive_lock() on buffer reserve - trace_recursive_unlock() on buffer commit However sometimes, we don't commit but discard on entry to the buffer, ie: in case of filter checking. Then we must also unlock the recursion protection on discard time, otherwise the tracing gets definitely deactivated and a warning is raised spuriously, such as: 111.119821] ------------[ cut here ]------------ [ 111.119829] WARNING: at kernel/trace/ring_buffer.c:1498 ring_buffer_lock_reserve+0x1b7/0x1d0() [ 111.119835] Hardware name: AMILO Li 2727 [ 111.119839] Modules linked in: [ 111.119846] Pid: 5731, comm: Xorg Tainted: G W 2.6.30-rc1 #69 [ 111.119851] Call Trace: [ 111.119863] [<ffffffff8025ce68>] warn_slowpath+0xd8/0x130 [ 111.119873] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0 [ 111.119882] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0 [ 111.119891] [<ffffffff802199b0>] ? native_sched_clock+0x20/0x70 [ 111.119899] [<ffffffff80286dee>] ? put_lock_stats+0xe/0x30 [ 111.119906] [<ffffffff80286eb8>] ? lock_release_holdtime+0xa8/0x150 [ 111.119913] [<ffffffff802c8ae7>] ring_buffer_lock_reserve+0x1b7/0x1d0 [ 111.119921] [<ffffffff802cd110>] trace_buffer_lock_reserve+0x30/0x70 [ 111.119930] [<ffffffff802ce000>] trace_current_buffer_lock_reserve+0x20/0x30 [ 111.119939] [<ffffffff802474e8>] ftrace_raw_event_sched_switch+0x58/0x100 [ 111.119948] [<ffffffff808103b7>] __schedule+0x3a7/0x4cd [ 111.119957] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.119964] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.119971] [<ffffffff80810c08>] schedule+0x18/0x40 [ 111.119977] [<ffffffff80810e09>] preempt_schedule+0x39/0x60 [ 111.119985] [<ffffffff80813bd3>] _read_unlock+0x53/0x60 [ 111.119993] [<ffffffff807259d2>] sock_def_readable+0x72/0x80 [ 111.120002] [<ffffffff807ad5ed>] unix_stream_sendmsg+0x24d/0x3d0 [ 111.120011] [<ffffffff807219a3>] sock_aio_write+0x143/0x160 [ 111.120019] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120026] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160 [ 111.120033] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160 [ 111.120042] [<ffffffff8031c283>] do_sync_readv_writev+0xf3/0x140 [ 111.120049] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120057] [<ffffffff80276ff0>] ? autoremove_wake_function+0x0/0x40 [ 111.120067] [<ffffffff8045d489>] ? cap_file_permission+0x9/0x10 [ 111.120074] [<ffffffff8045c1e6>] ? security_file_permission+0x16/0x20 [ 111.120082] [<ffffffff8031cab4>] do_readv_writev+0xd4/0x1f0 [ 111.120089] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120097] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120105] [<ffffffff8031cc18>] vfs_writev+0x48/0x70 [ 111.120111] [<ffffffff8031cd65>] sys_writev+0x55/0xc0 [ 111.120119] [<ffffffff80211e32>] system_call_fastpath+0x16/0x1b [ 111.120125] ---[ end trace 15605f4e98d5ccb5 ]--- [ Impact: fix spurious warning triggering tracing shutdown ] Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2009-04-20 05:39:33 +08:00
/* time delta must be non zero */
if (!event->time_delta)
event->time_delta = 1;
}
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
/*
* Decrement the entries to the page that an event is on.
* The event does not even need to exist, only the pointer
* to the page it is on. This may only be called before the commit
* takes place.
*/
static inline void
rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
unsigned long addr = (unsigned long)event;
struct buffer_page *bpage = cpu_buffer->commit_page;
struct buffer_page *start;
addr &= PAGE_MASK;
/* Do the likely case first */
if (likely(bpage->page == (void *)addr)) {
local_dec(&bpage->entries);
return;
}
/*
* Because the commit page may be on the reader page we
* start with the next page and check the end loop there.
*/
rb_inc_page(cpu_buffer, &bpage);
start = bpage;
do {
if (bpage->page == (void *)addr) {
local_dec(&bpage->entries);
return;
}
rb_inc_page(cpu_buffer, &bpage);
} while (bpage != start);
/* commit not part of this buffer?? */
RB_WARN_ON(cpu_buffer, 1);
}
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
/**
* ring_buffer_commit_discard - discard an event that has not been committed
* @buffer: the ring buffer
* @event: non committed event to discard
*
ring-buffer: remove ring_buffer_event_discard The function ring_buffer_event_discard can be used on any item in the ring buffer, even after the item was committed. This function provides no safety nets and is very race prone. An item may be safely removed from the ring buffer before it is committed with the ring_buffer_discard_commit. Since there are currently no users of this function, and because this function is racey and error prone, this patch removes it altogether. Note, removing this function also allows the counters to ignore all discarded events (patches will follow). Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-04 03:33:41 +08:00
* Sometimes an event that is in the ring buffer needs to be ignored.
* This function lets the user discard an event in the ring buffer
* and then that event will not be read later.
*
* This function only works if it is called before the the item has been
* committed. It will try to free the event from the ring buffer
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
* if another event has not been added behind it.
*
* If another event has been added behind it, it will set the event
* up as discarded, and perform the commit.
*
* If this function is called, do not call ring_buffer_unlock_commit on
* the event.
*/
void ring_buffer_discard_commit(struct ring_buffer *buffer,
struct ring_buffer_event *event)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu;
/* The event is discarded regardless */
tracing/ring-buffer: Add unlock recursion protection on discard The pair of helpers trace_recursive_lock() and trace_recursive_unlock() have been introduced recently to provide generic tracing recursion protection. They are used in a symetric way: - trace_recursive_lock() on buffer reserve - trace_recursive_unlock() on buffer commit However sometimes, we don't commit but discard on entry to the buffer, ie: in case of filter checking. Then we must also unlock the recursion protection on discard time, otherwise the tracing gets definitely deactivated and a warning is raised spuriously, such as: 111.119821] ------------[ cut here ]------------ [ 111.119829] WARNING: at kernel/trace/ring_buffer.c:1498 ring_buffer_lock_reserve+0x1b7/0x1d0() [ 111.119835] Hardware name: AMILO Li 2727 [ 111.119839] Modules linked in: [ 111.119846] Pid: 5731, comm: Xorg Tainted: G W 2.6.30-rc1 #69 [ 111.119851] Call Trace: [ 111.119863] [<ffffffff8025ce68>] warn_slowpath+0xd8/0x130 [ 111.119873] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0 [ 111.119882] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0 [ 111.119891] [<ffffffff802199b0>] ? native_sched_clock+0x20/0x70 [ 111.119899] [<ffffffff80286dee>] ? put_lock_stats+0xe/0x30 [ 111.119906] [<ffffffff80286eb8>] ? lock_release_holdtime+0xa8/0x150 [ 111.119913] [<ffffffff802c8ae7>] ring_buffer_lock_reserve+0x1b7/0x1d0 [ 111.119921] [<ffffffff802cd110>] trace_buffer_lock_reserve+0x30/0x70 [ 111.119930] [<ffffffff802ce000>] trace_current_buffer_lock_reserve+0x20/0x30 [ 111.119939] [<ffffffff802474e8>] ftrace_raw_event_sched_switch+0x58/0x100 [ 111.119948] [<ffffffff808103b7>] __schedule+0x3a7/0x4cd [ 111.119957] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.119964] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.119971] [<ffffffff80810c08>] schedule+0x18/0x40 [ 111.119977] [<ffffffff80810e09>] preempt_schedule+0x39/0x60 [ 111.119985] [<ffffffff80813bd3>] _read_unlock+0x53/0x60 [ 111.119993] [<ffffffff807259d2>] sock_def_readable+0x72/0x80 [ 111.120002] [<ffffffff807ad5ed>] unix_stream_sendmsg+0x24d/0x3d0 [ 111.120011] [<ffffffff807219a3>] sock_aio_write+0x143/0x160 [ 111.120019] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120026] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160 [ 111.120033] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160 [ 111.120042] [<ffffffff8031c283>] do_sync_readv_writev+0xf3/0x140 [ 111.120049] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120057] [<ffffffff80276ff0>] ? autoremove_wake_function+0x0/0x40 [ 111.120067] [<ffffffff8045d489>] ? cap_file_permission+0x9/0x10 [ 111.120074] [<ffffffff8045c1e6>] ? security_file_permission+0x16/0x20 [ 111.120082] [<ffffffff8031cab4>] do_readv_writev+0xd4/0x1f0 [ 111.120089] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120097] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120105] [<ffffffff8031cc18>] vfs_writev+0x48/0x70 [ 111.120111] [<ffffffff8031cd65>] sys_writev+0x55/0xc0 [ 111.120119] [<ffffffff80211e32>] system_call_fastpath+0x16/0x1b [ 111.120125] ---[ end trace 15605f4e98d5ccb5 ]--- [ Impact: fix spurious warning triggering tracing shutdown ] Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2009-04-20 05:39:33 +08:00
rb_event_discard(event);
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
cpu = smp_processor_id();
cpu_buffer = buffer->buffers[cpu];
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
/*
* This must only be called if the event has not been
* committed yet. Thus we can assume that preemption
* is still disabled.
*/
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
rb_decrement_entry(cpu_buffer, event);
ring-buffer: fix check of try_to_discard result The function ring_buffer_discard_commit inversed the code path of the result of try_to_discard. It should skip incrementing the entry counter if try_to_discard succeeded. But instead, it increments the entry conder if it succeeded to discard, and does not increment it if it fails. The result of this bug is that filtering will make the stat counters incorrect. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-08-06 00:02:48 +08:00
if (rb_try_to_discard(cpu_buffer, event))
ring-buffer: try to discard unneeded timestamps There are times that a race may happen that we add a timestamp in a nested write. This timestamp would just contain a zero delta and serves no purpose. Now that we have a way to discard events, this patch will try to discard the timestamp instead of just wasting the space in the ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 11:00:53 +08:00
goto out;
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
/*
* The commit is still visible by the reader, so we
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
* must still update the timestamp.
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
*/
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
rb_update_write_stamp(cpu_buffer, event);
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
out:
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
rb_end_commit(cpu_buffer);
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
tracing/ring-buffer: Add unlock recursion protection on discard The pair of helpers trace_recursive_lock() and trace_recursive_unlock() have been introduced recently to provide generic tracing recursion protection. They are used in a symetric way: - trace_recursive_lock() on buffer reserve - trace_recursive_unlock() on buffer commit However sometimes, we don't commit but discard on entry to the buffer, ie: in case of filter checking. Then we must also unlock the recursion protection on discard time, otherwise the tracing gets definitely deactivated and a warning is raised spuriously, such as: 111.119821] ------------[ cut here ]------------ [ 111.119829] WARNING: at kernel/trace/ring_buffer.c:1498 ring_buffer_lock_reserve+0x1b7/0x1d0() [ 111.119835] Hardware name: AMILO Li 2727 [ 111.119839] Modules linked in: [ 111.119846] Pid: 5731, comm: Xorg Tainted: G W 2.6.30-rc1 #69 [ 111.119851] Call Trace: [ 111.119863] [<ffffffff8025ce68>] warn_slowpath+0xd8/0x130 [ 111.119873] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0 [ 111.119882] [<ffffffff8028a30f>] ? __lock_acquire+0x19f/0x1ae0 [ 111.119891] [<ffffffff802199b0>] ? native_sched_clock+0x20/0x70 [ 111.119899] [<ffffffff80286dee>] ? put_lock_stats+0xe/0x30 [ 111.119906] [<ffffffff80286eb8>] ? lock_release_holdtime+0xa8/0x150 [ 111.119913] [<ffffffff802c8ae7>] ring_buffer_lock_reserve+0x1b7/0x1d0 [ 111.119921] [<ffffffff802cd110>] trace_buffer_lock_reserve+0x30/0x70 [ 111.119930] [<ffffffff802ce000>] trace_current_buffer_lock_reserve+0x20/0x30 [ 111.119939] [<ffffffff802474e8>] ftrace_raw_event_sched_switch+0x58/0x100 [ 111.119948] [<ffffffff808103b7>] __schedule+0x3a7/0x4cd [ 111.119957] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.119964] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.119971] [<ffffffff80810c08>] schedule+0x18/0x40 [ 111.119977] [<ffffffff80810e09>] preempt_schedule+0x39/0x60 [ 111.119985] [<ffffffff80813bd3>] _read_unlock+0x53/0x60 [ 111.119993] [<ffffffff807259d2>] sock_def_readable+0x72/0x80 [ 111.120002] [<ffffffff807ad5ed>] unix_stream_sendmsg+0x24d/0x3d0 [ 111.120011] [<ffffffff807219a3>] sock_aio_write+0x143/0x160 [ 111.120019] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120026] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160 [ 111.120033] [<ffffffff80721860>] ? sock_aio_write+0x0/0x160 [ 111.120042] [<ffffffff8031c283>] do_sync_readv_writev+0xf3/0x140 [ 111.120049] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120057] [<ffffffff80276ff0>] ? autoremove_wake_function+0x0/0x40 [ 111.120067] [<ffffffff8045d489>] ? cap_file_permission+0x9/0x10 [ 111.120074] [<ffffffff8045c1e6>] ? security_file_permission+0x16/0x20 [ 111.120082] [<ffffffff8031cab4>] do_readv_writev+0xd4/0x1f0 [ 111.120089] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120097] [<ffffffff80211b56>] ? ftrace_call+0x5/0x2b [ 111.120105] [<ffffffff8031cc18>] vfs_writev+0x48/0x70 [ 111.120111] [<ffffffff8031cd65>] sys_writev+0x55/0xc0 [ 111.120119] [<ffffffff80211e32>] system_call_fastpath+0x16/0x1b [ 111.120125] ---[ end trace 15605f4e98d5ccb5 ]--- [ Impact: fix spurious warning triggering tracing shutdown ] Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2009-04-20 05:39:33 +08:00
trace_recursive_unlock();
tracing: Remove ftrace_preempt_disable/enable The ftrace_preempt_disable/enable functions were to address a recursive race caused by the function tracer. The function tracer traces all functions which makes it easily susceptible to recursion. One area was preempt_enable(). This would call the scheduler and the schedulre would call the function tracer and loop. (So was it thought). The ftrace_preempt_disable/enable was made to protect against recursion inside the scheduler by storing the NEED_RESCHED flag. If it was set before the ftrace_preempt_disable() it would not call schedule on ftrace_preempt_enable(), thinking that if it was set before then it would have already scheduled unless it was already in the scheduler. This worked fine except in the case of SMP, where another task would set the NEED_RESCHED flag for a task on another CPU, and then kick off an IPI to trigger it. This could cause the NEED_RESCHED to be saved at ftrace_preempt_disable() but the IPI to arrive in the the preempt disabled section. The ftrace_preempt_enable() would not call the scheduler because the flag was already set before entring the section. This bug would cause a missed preemption check and cause lower latencies. Investigating further, I found that the recusion caused by the function tracer was not due to schedule(), but due to preempt_schedule(). Now that preempt_schedule is completely annotated with notrace, the recusion no longer is an issue. Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-06-03 21:36:50 +08:00
preempt_enable_notrace();
ring-buffer: add ring_buffer_discard_commit The ring_buffer_discard_commit is similar to ring_buffer_event_discard but it can only be done on an event that has yet to be commited. Unpredictable results can happen otherwise. The main difference between ring_buffer_discard_commit and ring_buffer_event_discard is that ring_buffer_discard_commit will try to free the data in the ring buffer if nothing has addded data after the reserved event. If something did, then it acts almost the same as ring_buffer_event_discard followed by a ring_buffer_unlock_commit. Note, either ring_buffer_commit_discard and ring_buffer_unlock_commit can be called on an event, not both. This commit also exports both discard functions to be usable by GPL modules. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-04-02 12:09:41 +08:00
}
EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_write - write data to the buffer without reserving
* @buffer: The ring buffer to write to.
* @length: The length of the data being written (excluding the event header)
* @data: The data to write to the buffer.
*
* This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
* one function. If you already have the data to write to the buffer, it
* may be easier to simply call this function.
*
* Note, like ring_buffer_lock_reserve, the length is the length of the data
* and not the length of the event which would hold the header.
*/
int ring_buffer_write(struct ring_buffer *buffer,
unsigned long length,
void *data)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
void *body;
int ret = -EBUSY;
tracing: Remove ftrace_preempt_disable/enable The ftrace_preempt_disable/enable functions were to address a recursive race caused by the function tracer. The function tracer traces all functions which makes it easily susceptible to recursion. One area was preempt_enable(). This would call the scheduler and the schedulre would call the function tracer and loop. (So was it thought). The ftrace_preempt_disable/enable was made to protect against recursion inside the scheduler by storing the NEED_RESCHED flag. If it was set before the ftrace_preempt_disable() it would not call schedule on ftrace_preempt_enable(), thinking that if it was set before then it would have already scheduled unless it was already in the scheduler. This worked fine except in the case of SMP, where another task would set the NEED_RESCHED flag for a task on another CPU, and then kick off an IPI to trigger it. This could cause the NEED_RESCHED to be saved at ftrace_preempt_disable() but the IPI to arrive in the the preempt disabled section. The ftrace_preempt_enable() would not call the scheduler because the flag was already set before entring the section. This bug would cause a missed preemption check and cause lower latencies. Investigating further, I found that the recusion caused by the function tracer was not due to schedule(), but due to preempt_schedule(). Now that preempt_schedule is completely annotated with notrace, the recusion no longer is an issue. Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-06-03 21:36:50 +08:00
int cpu;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: add tracing_off_permanent Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-22 01:41:55 +08:00
if (ring_buffer_flags != RB_BUFFERS_ON)
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
return -EBUSY;
tracing: Remove ftrace_preempt_disable/enable The ftrace_preempt_disable/enable functions were to address a recursive race caused by the function tracer. The function tracer traces all functions which makes it easily susceptible to recursion. One area was preempt_enable(). This would call the scheduler and the schedulre would call the function tracer and loop. (So was it thought). The ftrace_preempt_disable/enable was made to protect against recursion inside the scheduler by storing the NEED_RESCHED flag. If it was set before the ftrace_preempt_disable() it would not call schedule on ftrace_preempt_enable(), thinking that if it was set before then it would have already scheduled unless it was already in the scheduler. This worked fine except in the case of SMP, where another task would set the NEED_RESCHED flag for a task on another CPU, and then kick off an IPI to trigger it. This could cause the NEED_RESCHED to be saved at ftrace_preempt_disable() but the IPI to arrive in the the preempt disabled section. The ftrace_preempt_enable() would not call the scheduler because the flag was already set before entring the section. This bug would cause a missed preemption check and cause lower latencies. Investigating further, I found that the recusion caused by the function tracer was not due to schedule(), but due to preempt_schedule(). Now that preempt_schedule is completely annotated with notrace, the recusion no longer is an issue. Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-06-03 21:36:50 +08:00
preempt_disable_notrace();
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
ring-buffer: Move disabled check into preempt disable section The ring buffer resizing and resetting relies on a schedule RCU action. The buffers are disabled, a synchronize_sched() is called and then the resize or reset takes place. But this only works if the disabling of the buffers are within the preempt disabled section, otherwise a window exists that the buffers can be written to while a reset or resize takes place. Cc: stable@kernel.org Reported-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <4B949E43.2010906@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-03-08 14:50:43 +08:00
if (atomic_read(&buffer->record_disabled))
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu = raw_smp_processor_id();
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer = buffer->buffers[cpu];
if (atomic_read(&cpu_buffer->record_disabled))
goto out;
ring-buffer: move calculation of event length The event length is calculated and passed in to rb_reserve_next_event in two different locations. Having rb_reserve_next_event do the calculations directly makes only one location to do the change and causes the calculation to be inlined by gcc. Before: text data bss dec hex filename 16538 24 12 16574 40be kernel/trace/ring_buffer.o After: text data bss dec hex filename 16490 24 12 16526 408e kernel/trace/ring_buffer.o [ Impact: smaller more efficient code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-12 02:42:53 +08:00
if (length > BUF_MAX_DATA_SIZE)
goto out;
ring-buffer: check for swapped buffers in start of committing Because the irqsoff tracer can swap an internal CPU buffer, it is possible that a swap happens between the start of the write and before the committing bit is set (the committing bit will disable swapping). This patch adds a check for this and will fail the write if it detects it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-05 02:11:34 +08:00
event = rb_reserve_next_event(buffer, cpu_buffer, length);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
if (!event)
goto out;
body = rb_event_data(event);
memcpy(body, data, length);
rb_commit(cpu_buffer, event);
ret = 0;
out:
tracing: Remove ftrace_preempt_disable/enable The ftrace_preempt_disable/enable functions were to address a recursive race caused by the function tracer. The function tracer traces all functions which makes it easily susceptible to recursion. One area was preempt_enable(). This would call the scheduler and the schedulre would call the function tracer and loop. (So was it thought). The ftrace_preempt_disable/enable was made to protect against recursion inside the scheduler by storing the NEED_RESCHED flag. If it was set before the ftrace_preempt_disable() it would not call schedule on ftrace_preempt_enable(), thinking that if it was set before then it would have already scheduled unless it was already in the scheduler. This worked fine except in the case of SMP, where another task would set the NEED_RESCHED flag for a task on another CPU, and then kick off an IPI to trigger it. This could cause the NEED_RESCHED to be saved at ftrace_preempt_disable() but the IPI to arrive in the the preempt disabled section. The ftrace_preempt_enable() would not call the scheduler because the flag was already set before entring the section. This bug would cause a missed preemption check and cause lower latencies. Investigating further, I found that the recusion caused by the function tracer was not due to schedule(), but due to preempt_schedule(). Now that preempt_schedule is completely annotated with notrace, the recusion no longer is an issue. Reported-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-06-03 21:36:50 +08:00
preempt_enable_notrace();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return ret;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_write);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
kernel/trace/ring_buffer.c: reduce inlining text data bss dec hex filename before: 11320 228 8 11556 2d24 kernel/trace/ring_buffer.o after: 10592 228 8 10828 2a4c kernel/trace/ring_buffer.o Also: free_page(0) is legal. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-10 04:27:09 +08:00
static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
{
struct buffer_page *reader = cpu_buffer->reader_page;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
struct buffer_page *head = rb_set_head_page(cpu_buffer);
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
struct buffer_page *commit = cpu_buffer->commit_page;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/* In case of error, head will be NULL */
if (unlikely(!head))
return 1;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
return reader->read == rb_page_commit(reader) &&
(commit == reader ||
(commit == head &&
head->read == rb_page_commit(commit)));
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_record_disable - stop all writes into the buffer
* @buffer: The ring buffer to stop writes to.
*
* This prevents all writes to the buffer. Any attempt to write
* to the buffer after this will fail and return NULL.
*
* The caller should call synchronize_sched() after this.
*/
void ring_buffer_record_disable(struct ring_buffer *buffer)
{
atomic_inc(&buffer->record_disabled);
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_record_enable - enable writes to the buffer
* @buffer: The ring buffer to enable writes
*
* Note, multiple disables will need the same number of enables
Fix misspellings of "truly" in comments. Some comments misspell "truly"; this fixes them. No code changes. Signed-off-by: Adam Buchbinder <adam.buchbinder@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2009-12-12 05:35:39 +08:00
* to truly enable the writing (much like preempt_disable).
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
*/
void ring_buffer_record_enable(struct ring_buffer *buffer)
{
atomic_dec(&buffer->record_disabled);
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
* @buffer: The ring buffer to stop writes to.
* @cpu: The CPU buffer to stop
*
* This prevents all writes to the buffer. Any attempt to write
* to the buffer after this will fail and return NULL.
*
* The caller should call synchronize_sched() after this.
*/
void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
return;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer = buffer->buffers[cpu];
atomic_inc(&cpu_buffer->record_disabled);
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_record_enable_cpu - enable writes to the buffer
* @buffer: The ring buffer to enable writes
* @cpu: The CPU to enable.
*
* Note, multiple disables will need the same number of enables
Fix misspellings of "truly" in comments. Some comments misspell "truly"; this fixes them. No code changes. Signed-off-by: Adam Buchbinder <adam.buchbinder@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2009-12-12 05:35:39 +08:00
* to truly enable the writing (much like preempt_disable).
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
*/
void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
return;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer = buffer->buffers[cpu];
atomic_dec(&cpu_buffer->record_disabled);
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_entries_cpu - get the number of entries in a cpu buffer
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the entries from.
*/
unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
unsigned long ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
return 0;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer = buffer->buffers[cpu];
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
ret = (local_read(&cpu_buffer->entries) - local_read(&cpu_buffer->overrun))
ring-buffer: convert cpu buffer entries to local_t The entries counter in cpu buffer is not atomic. It can be updated by other interrupts or from another CPU (readers). But making entries into "atomic_t" causes an atomic operation that can hurt performance. Instead we convert it to a local_t that will increment a counter with a local CPU atomic operation (if the arch supports it). Instead of fighting with readers and overwrites that decrement the counter, I added a "read" counter. Every time a reader reads an entry it is incremented. We already have a overrun counter and with that, the entries counter and the read counter, we can calculate the total number of entries in the buffer with: (entries - overrun) - read As long as the total number of entries in the ring buffer is less than the word size, this will work. But since the entries counter was previously a long, this is no different than what we had before. Thanks to Andrew Morton for pointing out in the first version that atomic_t does not replace unsigned long. I switched to atomic_long_t even though it is signed. A negative count is most likely a bug. [ Impact: keep accurate count of cpu buffer entries ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-01 08:49:44 +08:00
- cpu_buffer->read;
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
return ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the number of overruns from
*/
unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
unsigned long ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
return 0;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer = buffer->buffers[cpu];
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
ret = local_read(&cpu_buffer->overrun);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
return ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: add counters for commit overrun and nmi dropped entries The WARN_ON in the ring buffer when a commit is preempted and the buffer is filled by preceding writes can happen in normal operations. The WARN_ON makes it look like a bug, not to mention, because it does not stop tracing and calls printk which can also recurse, this is prone to deadlock (the WARN_ON is not in a position to recurse). This patch removes the WARN_ON and replaces it with a counter that can be retrieved by a tracer. This counter is called commit_overrun. While at it, I added a nmi_dropped counter to count any time an NMI entry is dropped because the NMI could not take the spinlock. [ Impact: prevent deadlock by printing normal case warning ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-30 01:43:37 +08:00
/**
* ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the number of overruns from
*/
unsigned long
ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
ret = local_read(&cpu_buffer->commit_overrun);
ring-buffer: add counters for commit overrun and nmi dropped entries The WARN_ON in the ring buffer when a commit is preempted and the buffer is filled by preceding writes can happen in normal operations. The WARN_ON makes it look like a bug, not to mention, because it does not stop tracing and calls printk which can also recurse, this is prone to deadlock (the WARN_ON is not in a position to recurse). This patch removes the WARN_ON and replaces it with a counter that can be retrieved by a tracer. This counter is called commit_overrun. While at it, I added a nmi_dropped counter to count any time an NMI entry is dropped because the NMI could not take the spinlock. [ Impact: prevent deadlock by printing normal case warning ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-30 01:43:37 +08:00
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_entries - get the number of entries in a buffer
* @buffer: The ring buffer
*
* Returns the total number of entries in the ring buffer
* (all CPU entries)
*/
unsigned long ring_buffer_entries(struct ring_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long entries = 0;
int cpu;
/* if you care about this being correct, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
ring-buffer: convert cpu buffer entries to local_t The entries counter in cpu buffer is not atomic. It can be updated by other interrupts or from another CPU (readers). But making entries into "atomic_t" causes an atomic operation that can hurt performance. Instead we convert it to a local_t that will increment a counter with a local CPU atomic operation (if the arch supports it). Instead of fighting with readers and overwrites that decrement the counter, I added a "read" counter. Every time a reader reads an entry it is incremented. We already have a overrun counter and with that, the entries counter and the read counter, we can calculate the total number of entries in the buffer with: (entries - overrun) - read As long as the total number of entries in the ring buffer is less than the word size, this will work. But since the entries counter was previously a long, this is no different than what we had before. Thanks to Andrew Morton for pointing out in the first version that atomic_t does not replace unsigned long. I switched to atomic_long_t even though it is signed. A negative count is most likely a bug. [ Impact: keep accurate count of cpu buffer entries ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-01 08:49:44 +08:00
entries += (local_read(&cpu_buffer->entries) -
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
local_read(&cpu_buffer->overrun)) - cpu_buffer->read;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
return entries;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_entries);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
tracing: Fix comment typo and documentation example Trivial patch to fix a documentation example and to fix a comment. Signed-off-by: Jiri Olsa <jolsa@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20091023233646.871719877@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-10-24 07:36:18 +08:00
* ring_buffer_overruns - get the number of overruns in buffer
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
* @buffer: The ring buffer
*
* Returns the total number of overruns in the ring buffer
* (all CPU entries)
*/
unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long overruns = 0;
int cpu;
/* if you care about this being correct, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
overruns += local_read(&cpu_buffer->overrun);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
return overruns;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_overruns);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: fix deadlock from reader_lock in read_start Impact: deadlock fix in ring_buffer_read_start The ring_buffer_iter_reset was called from ring_buffer_read_start where both grabbed the reader_lock. This patch separates out the internals of ring_buffer_iter_reset to its own function so that both APIs may grab the reader_lock. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 13:01:26 +08:00
static void rb_iter_reset(struct ring_buffer_iter *iter)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
/* Iterator usage is expected to have record disabled */
if (list_empty(&cpu_buffer->reader_page->list)) {
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
iter->head_page = rb_set_head_page(cpu_buffer);
if (unlikely(!iter->head_page))
return;
iter->head = iter->head_page->read;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
} else {
iter->head_page = cpu_buffer->reader_page;
ring-buffer: move page indexes into page headers Remove the global head and tail indexes and move them into the page header. Each page will now keep track of where the last write and read was made. We also rename the head and tail to read and write for better clarification. This patch is needed for future enhancements to move the ring buffer to a lockless solution. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:58 +08:00
iter->head = cpu_buffer->reader_page->read;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
}
if (iter->head)
iter->read_stamp = cpu_buffer->read_stamp;
else
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
iter->read_stamp = iter->head_page->page->time_stamp;
ring-buffer: Check if ring buffer iterator has stale data Usually reads of the ring buffer is performed by a single task. There are two types of reads from the ring buffer. One is a consuming read which will consume the entry that was read and the next read will be the entry that follows. The other is an iterator that will let the user read the contents of the ring buffer without modifying it. When an iterator is allocated, writes to the ring buffer are disabled to protect the iterator. The problem exists when consuming reads happen while an iterator is allocated. Specifically, the kind of read that swaps out an entire page (used by splice) and replaces it with a new read. If the iterator is on the page that is swapped out, then the next read may read from this swapped out page and return garbage. This patch adds a check when reading the iterator to make sure that the iterator contents are still valid. If a consuming read has taken place, the iterator is reset. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-01-26 04:17:47 +08:00
iter->cache_reader_page = cpu_buffer->reader_page;
iter->cache_read = cpu_buffer->read;
ring-buffer: fix deadlock from reader_lock in read_start Impact: deadlock fix in ring_buffer_read_start The ring_buffer_iter_reset was called from ring_buffer_read_start where both grabbed the reader_lock. This patch separates out the internals of ring_buffer_iter_reset to its own function so that both APIs may grab the reader_lock. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 13:01:26 +08:00
}
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
ring-buffer: fix deadlock from reader_lock in read_start Impact: deadlock fix in ring_buffer_read_start The ring_buffer_iter_reset was called from ring_buffer_read_start where both grabbed the reader_lock. This patch separates out the internals of ring_buffer_iter_reset to its own function so that both APIs may grab the reader_lock. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 13:01:26 +08:00
/**
* ring_buffer_iter_reset - reset an iterator
* @iter: The iterator to reset
*
* Resets the iterator, so that it will start from the beginning
* again.
*/
void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
{
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
struct ring_buffer_per_cpu *cpu_buffer;
ring-buffer: fix deadlock from reader_lock in read_start Impact: deadlock fix in ring_buffer_read_start The ring_buffer_iter_reset was called from ring_buffer_read_start where both grabbed the reader_lock. This patch separates out the internals of ring_buffer_iter_reset to its own function so that both APIs may grab the reader_lock. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 13:01:26 +08:00
unsigned long flags;
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
if (!iter)
return;
cpu_buffer = iter->cpu_buffer;
ring-buffer: fix deadlock from reader_lock in read_start Impact: deadlock fix in ring_buffer_read_start The ring_buffer_iter_reset was called from ring_buffer_read_start where both grabbed the reader_lock. This patch separates out the internals of ring_buffer_iter_reset to its own function so that both APIs may grab the reader_lock. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 13:01:26 +08:00
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_iter_reset(iter);
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_iter_empty - check if an iterator has no more to read
* @iter: The iterator to check
*/
int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer;
cpu_buffer = iter->cpu_buffer;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
return iter->head_page == cpu_buffer->commit_page &&
iter->head == rb_commit_index(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
static void
rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
u64 delta;
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
switch (event->type_len) {
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
case RINGBUF_TYPE_PADDING:
return;
case RINGBUF_TYPE_TIME_EXTEND:
delta = event->array[0];
delta <<= TS_SHIFT;
delta += event->time_delta;
cpu_buffer->read_stamp += delta;
return;
case RINGBUF_TYPE_TIME_STAMP:
/* FIXME: not implemented */
return;
case RINGBUF_TYPE_DATA:
cpu_buffer->read_stamp += event->time_delta;
return;
default:
BUG();
}
return;
}
static void
rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
struct ring_buffer_event *event)
{
u64 delta;
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
switch (event->type_len) {
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
case RINGBUF_TYPE_PADDING:
return;
case RINGBUF_TYPE_TIME_EXTEND:
delta = event->array[0];
delta <<= TS_SHIFT;
delta += event->time_delta;
iter->read_stamp += delta;
return;
case RINGBUF_TYPE_TIME_STAMP:
/* FIXME: not implemented */
return;
case RINGBUF_TYPE_DATA:
iter->read_stamp += event->time_delta;
return;
default:
BUG();
}
return;
}
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
static struct buffer_page *
rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
struct buffer_page *reader = NULL;
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
unsigned long overwrite;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
unsigned long flags;
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
int nr_loops = 0;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
int ret;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
ring-buffer: convert to raw spinlocks Impact: no lockdep debugging of ring buffer The problem with running lockdep on the ring buffer is that the ring buffer is the core infrastructure of ftrace. What happens is that the tracer will start tracing the lockdep code while lockdep is testing the ring buffers locks. This can cause lockdep to fail due to testing cases that have not fully finished their locking transition. This patch converts the spin locks used by the ring buffer back into raw spin locks which lockdep does not check. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-06 13:09:43 +08:00
local_irq_save(flags);
locking: Convert __raw_spin* functions to arch_spin* Name space cleanup. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: linux-arch@vger.kernel.org
2009-12-03 03:01:25 +08:00
arch_spin_lock(&cpu_buffer->lock);
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
again:
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
/*
* This should normally only loop twice. But because the
* start of the reader inserts an empty page, it causes
* a case where we will loop three times. There should be no
* reason to loop four times (that I know of).
*/
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
reader = NULL;
goto out;
}
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
reader = cpu_buffer->reader_page;
/* If there's more to read, return this page */
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
if (cpu_buffer->reader_page->read < rb_page_size(reader))
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
goto out;
/* Never should we have an index greater than the size */
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
if (RB_WARN_ON(cpu_buffer,
cpu_buffer->reader_page->read > rb_page_size(reader)))
goto out;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
/* check if we caught up to the tail */
reader = NULL;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
if (cpu_buffer->commit_page == cpu_buffer->reader_page)
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/*
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
* Reset the reader page to size zero.
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
*/
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
local_set(&cpu_buffer->reader_page->write, 0);
local_set(&cpu_buffer->reader_page->entries, 0);
local_set(&cpu_buffer->reader_page->page->commit, 0);
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
cpu_buffer->reader_page->real_end = 0;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
spin:
/*
* Splice the empty reader page into the list around the head.
*/
reader = rb_set_head_page(cpu_buffer);
ring-buffer: Add rb_list_head() wrapper around new reader page next field If the very unlikely case happens where the writer moves the head by one between where the head page is read and where the new reader page is assigned _and_ the writer then writes and wraps the entire ring buffer so that the head page is back to what was originally read as the head page, the page to be swapped will have a corrupted next pointer. Simple solution is to wrap the assignment of the next pointer with a rb_list_head(). Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-01-07 09:40:44 +08:00
cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
cpu_buffer->reader_page->list.prev = reader->list.prev;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
/*
* cpu_buffer->pages just needs to point to the buffer, it
* has no specific buffer page to point to. Lets move it out
* of our way so we don't accidently swap it.
*/
cpu_buffer->pages = reader->list.prev;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/* The reader page will be pointing to the new head */
rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
/*
* We want to make sure we read the overruns after we set up our
* pointers to the next object. The writer side does a
* cmpxchg to cross pages which acts as the mb on the writer
* side. Note, the reader will constantly fail the swap
* while the writer is updating the pointers, so this
* guarantees that the overwrite recorded here is the one we
* want to compare with the last_overrun.
*/
smp_mb();
overwrite = local_read(&(cpu_buffer->overrun));
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/*
* Here's the tricky part.
*
* We need to move the pointer past the header page.
* But we can only do that if a writer is not currently
* moving it. The page before the header page has the
* flag bit '1' set if it is pointing to the page we want.
* but if the writer is in the process of moving it
* than it will be '2' or already moved '0'.
*/
ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/*
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
* If we did not convert it, then we must try again.
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
*/
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
if (!ret)
goto spin;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
/*
* Yeah! We succeeded in replacing the page.
*
* Now make the new head point back to the reader page.
*/
ring-buffer: Wrap a list.next reference with rb_list_head() This reference at the end of rb_get_reader_page() was causing off-by-one writes to the prev pointer of the page after the reader page when that page is the head page, and therefore the reader page has the RB_PAGE_HEAD flag in its list.next pointer. This eventually results in a GPF in a subsequent call to rb_set_head_page() (usually from rb_get_reader_page()) when that prev pointer is dereferenced. The dereferenced register would characteristically have an address that appears shifted left by one byte (eg, ffxxxxxxxxxxxxyy instead of ffffxxxxxxxxxxxx) due to being written at an address one byte too high. Signed-off-by: David Sharp <dhsharp@google.com> LKML-Reference: <1262826727-9090-1-git-send-email-dhsharp@google.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-01-07 09:12:07 +08:00
rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
/* Finally update the reader page to the new head */
cpu_buffer->reader_page = reader;
rb_reset_reader_page(cpu_buffer);
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
if (overwrite != cpu_buffer->last_overrun) {
cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
cpu_buffer->last_overrun = overwrite;
}
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
goto again;
out:
locking: Convert __raw_spin* functions to arch_spin* Name space cleanup. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: linux-arch@vger.kernel.org
2009-12-03 03:01:25 +08:00
arch_spin_unlock(&cpu_buffer->lock);
ring-buffer: convert to raw spinlocks Impact: no lockdep debugging of ring buffer The problem with running lockdep on the ring buffer is that the ring buffer is the core infrastructure of ftrace. What happens is that the tracer will start tracing the lockdep code while lockdep is testing the ring buffers locks. This can cause lockdep to fail due to testing cases that have not fully finished their locking transition. This patch converts the spin locks used by the ring buffer back into raw spin locks which lockdep does not check. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-06 13:09:43 +08:00
local_irq_restore(flags);
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
return reader;
}
static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
{
struct ring_buffer_event *event;
struct buffer_page *reader;
unsigned length;
reader = rb_get_reader_page(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
/* This function should not be called when buffer is empty */
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
if (RB_WARN_ON(cpu_buffer, !reader))
return;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
event = rb_reader_event(cpu_buffer);
ring-buffer: do not count discarded events The latency tracers report the number of items in the trace buffer. This uses the ring buffer data to calculate this. Because discarded events are also counted, the numbers do not match the number of items that are printed. The ring buffer also adds a "padding" item to the end of each buffer page which also gets counted as a discarded item. This patch decrements the counter to the page entries on a discard. This allows us to ignore discarded entries while reading the buffer. Decrementing the counter is still safe since it can only happen while the committing flag is still set. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:23:58 +08:00
if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
ring-buffer: convert cpu buffer entries to local_t The entries counter in cpu buffer is not atomic. It can be updated by other interrupts or from another CPU (readers). But making entries into "atomic_t" causes an atomic operation that can hurt performance. Instead we convert it to a local_t that will increment a counter with a local CPU atomic operation (if the arch supports it). Instead of fighting with readers and overwrites that decrement the counter, I added a "read" counter. Every time a reader reads an entry it is incremented. We already have a overrun counter and with that, the entries counter and the read counter, we can calculate the total number of entries in the buffer with: (entries - overrun) - read As long as the total number of entries in the ring buffer is less than the word size, this will work. But since the entries counter was previously a long, this is no different than what we had before. Thanks to Andrew Morton for pointing out in the first version that atomic_t does not replace unsigned long. I switched to atomic_long_t even though it is signed. A negative count is most likely a bug. [ Impact: keep accurate count of cpu buffer entries ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-01 08:49:44 +08:00
cpu_buffer->read++;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
rb_update_read_stamp(cpu_buffer, event);
length = rb_event_length(event);
ring-buffer: move page indexes into page headers Remove the global head and tail indexes and move them into the page header. Each page will now keep track of where the last write and read was made. We also rename the head and tail to read and write for better clarification. This patch is needed for future enhancements to move the ring buffer to a lockless solution. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:58 +08:00
cpu_buffer->reader_page->read += length;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
static void rb_advance_iter(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
unsigned length;
cpu_buffer = iter->cpu_buffer;
/*
* Check if we are at the end of the buffer.
*/
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
if (iter->head >= rb_page_size(iter->head_page)) {
ring-buffer: discard timestamps that are at the start of the buffer Every buffer page in the ring buffer includes its own time stamp. When an event is recorded to the ring buffer with a delta time greater than what can be held in the event header, a time stamp event is created. If the the create timestamp falls over to the next buffer page, it is redundant because the buffer page holds a full time stamp. This patch will try to discard the time stamp when it falls to the start of the next page. This change also fixes a issues with disarding events. If most events are discarded, timestamps will start to creep into the ring buffer. If we do not discard the timestamps then they can fill up the ring buffer over time and waste space. This change will keep time stamps from filling up over another page. If something is recorded in the buffer page, and the rest is filtered, then the time stamps can only fill up to the end of the page. [ Impact: prevent time stamps from filling ring buffer ] Reported-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 21:30:10 +08:00
/* discarded commits can make the page empty */
if (iter->head_page == cpu_buffer->commit_page)
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
return;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
rb_inc_iter(iter);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return;
}
event = rb_iter_head_event(iter);
length = rb_event_length(event);
/*
* This should not be called to advance the header if we are
* at the tail of the buffer.
*/
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
if (RB_WARN_ON(cpu_buffer,
ring-buffer: replace most bug ons with warn on and disable buffer This patch replaces most of the BUG_ONs in the ring_buffer code with RB_WARN_ON variants. It adds some more variants as needed for the replacement. This lets the buffer die nicely and still warn the user. One BUG_ON remains in the code, and that is because it detects a bad pointer passed in by the calling function, and not a bug by the ring buffer code itself. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-11 12:07:30 +08:00
(iter->head_page == cpu_buffer->commit_page) &&
ring-buffer: clean up warn ons Impact: Restructure WARN_ONs in ring_buffer.c The current WARN_ON macros in ring_buffer.c are quite ugly. This patch cleans them up and uses a single RB_WARN_ON that returns the value of the condition. This allows the caller to abort the function if the condition is true. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 04:28:41 +08:00
(iter->head + length > rb_commit_index(cpu_buffer))))
return;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
rb_update_iter_read_stamp(iter, event);
iter->head += length;
/* check for end of page padding */
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
if ((iter->head >= rb_page_size(iter->head_page)) &&
(iter->head_page != cpu_buffer->commit_page))
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
rb_advance_iter(iter);
}
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
{
return cpu_buffer->lost_events;
}
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
static struct ring_buffer_event *
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
unsigned long *lost_events)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
struct ring_buffer_event *event;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
struct buffer_page *reader;
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
int nr_loops = 0;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
again:
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
/*
* We repeat when a timestamp is encountered. It is possible
* to get multiple timestamps from an interrupt entering just
ring-buffer: discard timestamps that are at the start of the buffer Every buffer page in the ring buffer includes its own time stamp. When an event is recorded to the ring buffer with a delta time greater than what can be held in the event header, a time stamp event is created. If the the create timestamp falls over to the next buffer page, it is redundant because the buffer page holds a full time stamp. This patch will try to discard the time stamp when it falls to the start of the next page. This change also fixes a issues with disarding events. If most events are discarded, timestamps will start to creep into the ring buffer. If we do not discard the timestamps then they can fill up the ring buffer over time and waste space. This change will keep time stamps from filling up over another page. If something is recorded in the buffer page, and the rest is filtered, then the time stamps can only fill up to the end of the page. [ Impact: prevent time stamps from filling ring buffer ] Reported-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 21:30:10 +08:00
* as one timestamp is about to be written, or from discarded
* commits. The most that we can have is the number on a single page.
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
*/
ring-buffer: discard timestamps that are at the start of the buffer Every buffer page in the ring buffer includes its own time stamp. When an event is recorded to the ring buffer with a delta time greater than what can be held in the event header, a time stamp event is created. If the the create timestamp falls over to the next buffer page, it is redundant because the buffer page holds a full time stamp. This patch will try to discard the time stamp when it falls to the start of the next page. This change also fixes a issues with disarding events. If most events are discarded, timestamps will start to creep into the ring buffer. If we do not discard the timestamps then they can fill up the ring buffer over time and waste space. This change will keep time stamps from filling up over another page. If something is recorded in the buffer page, and the rest is filtered, then the time stamps can only fill up to the end of the page. [ Impact: prevent time stamps from filling ring buffer ] Reported-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 21:30:10 +08:00
if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
return NULL;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
reader = rb_get_reader_page(cpu_buffer);
if (!reader)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return NULL;
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
event = rb_reader_event(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
switch (event->type_len) {
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
case RINGBUF_TYPE_PADDING:
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
if (rb_null_event(event))
RB_WARN_ON(cpu_buffer, 1);
/*
* Because the writer could be discarding every
* event it creates (which would probably be bad)
* if we were to go back to "again" then we may never
* catch up, and will trigger the warn on, or lock
* the box. Return the padding, and we will release
* the current locks, and try again.
*/
return event;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
rb_advance_reader(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
goto again;
case RINGBUF_TYPE_TIME_STAMP:
/* FIXME: not implemented */
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
rb_advance_reader(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
goto again;
case RINGBUF_TYPE_DATA:
if (ts) {
*ts = cpu_buffer->read_stamp + event->time_delta;
ring-buffer: consolidate interface of rb_buffer_peek() rb_buffer_peek() operates with struct ring_buffer_per_cpu *cpu_buffer only. Thus, instead of passing variables buffer and cpu it is better to use cpu_buffer directly. This also reduces the risk of races since cpu_buffer is not calculated twice. Signed-off-by: Robert Richter <robert.richter@amd.com> LKML-Reference: <1249045084-3028-1-git-send-email-robert.richter@amd.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-07-31 20:58:04 +08:00
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
ring-buffer: add api to allow a tracer to change clock source This patch adds a new function called ring_buffer_set_clock that allows a tracer to assign its own clock source to the buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-18 05:22:06 +08:00
cpu_buffer->cpu, ts);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
if (lost_events)
*lost_events = rb_lost_events(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return event;
default:
BUG();
}
return NULL;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_peek);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
static struct ring_buffer_event *
rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
struct ring_buffer *buffer;
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
int nr_loops = 0;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer = iter->cpu_buffer;
buffer = cpu_buffer->buffer;
ring-buffer: Check if ring buffer iterator has stale data Usually reads of the ring buffer is performed by a single task. There are two types of reads from the ring buffer. One is a consuming read which will consume the entry that was read and the next read will be the entry that follows. The other is an iterator that will let the user read the contents of the ring buffer without modifying it. When an iterator is allocated, writes to the ring buffer are disabled to protect the iterator. The problem exists when consuming reads happen while an iterator is allocated. Specifically, the kind of read that swaps out an entire page (used by splice) and replaces it with a new read. If the iterator is on the page that is swapped out, then the next read may read from this swapped out page and return garbage. This patch adds a check when reading the iterator to make sure that the iterator contents are still valid. If a consuming read has taken place, the iterator is reset. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-01-26 04:17:47 +08:00
/*
* Check if someone performed a consuming read to
* the buffer. A consuming read invalidates the iterator
* and we need to reset the iterator in this case.
*/
if (unlikely(iter->cache_read != cpu_buffer->read ||
iter->cache_reader_page != cpu_buffer->reader_page))
rb_iter_reset(iter);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
again:
ring-buffer: Check for end of page in iterator If the iterator comes to an empty page for some reason, or if the page is emptied by a consuming read. The iterator code currently does not check if the iterator is pass the contents, and may return a false entry. This patch adds a check to the ring buffer iterator to test if the current page has been completely read and sets the iterator to the next page if necessary. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-01-27 05:14:08 +08:00
if (ring_buffer_iter_empty(iter))
return NULL;
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
/*
ring-buffer: discard timestamps that are at the start of the buffer Every buffer page in the ring buffer includes its own time stamp. When an event is recorded to the ring buffer with a delta time greater than what can be held in the event header, a time stamp event is created. If the the create timestamp falls over to the next buffer page, it is redundant because the buffer page holds a full time stamp. This patch will try to discard the time stamp when it falls to the start of the next page. This change also fixes a issues with disarding events. If most events are discarded, timestamps will start to creep into the ring buffer. If we do not discard the timestamps then they can fill up the ring buffer over time and waste space. This change will keep time stamps from filling up over another page. If something is recorded in the buffer page, and the rest is filtered, then the time stamps can only fill up to the end of the page. [ Impact: prevent time stamps from filling ring buffer ] Reported-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 21:30:10 +08:00
* We repeat when a timestamp is encountered.
* We can get multiple timestamps by nested interrupts or also
* if filtering is on (discarding commits). Since discarding
* commits can be frequent we can get a lot of timestamps.
* But we limit them by not adding timestamps if they begin
* at the start of a page.
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
*/
ring-buffer: discard timestamps that are at the start of the buffer Every buffer page in the ring buffer includes its own time stamp. When an event is recorded to the ring buffer with a delta time greater than what can be held in the event header, a time stamp event is created. If the the create timestamp falls over to the next buffer page, it is redundant because the buffer page holds a full time stamp. This patch will try to discard the time stamp when it falls to the start of the next page. This change also fixes a issues with disarding events. If most events are discarded, timestamps will start to creep into the ring buffer. If we do not discard the timestamps then they can fill up the ring buffer over time and waste space. This change will keep time stamps from filling up over another page. If something is recorded in the buffer page, and the rest is filtered, then the time stamps can only fill up to the end of the page. [ Impact: prevent time stamps from filling ring buffer ] Reported-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-03 21:30:10 +08:00
if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
tracing, ring-buffer: add paranoid checks for loops While writing a new tracer, I had a bug where I caused the ring-buffer to recurse in a bad way. The bug was with the tracer I was writing and not the ring-buffer itself. But it took a long time to find the problem. This patch adds paranoid checks into the ring-buffer infrastructure that will catch bugs of this nature. Note: I put the bug back in the tracer and this patch showed the error nicely and prevented the lockup. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-31 21:58:35 +08:00
return NULL;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
if (rb_per_cpu_empty(cpu_buffer))
return NULL;
ring-buffer: Check for end of page in iterator If the iterator comes to an empty page for some reason, or if the page is emptied by a consuming read. The iterator code currently does not check if the iterator is pass the contents, and may return a false entry. This patch adds a check to the ring buffer iterator to test if the current page has been completely read and sets the iterator to the next page if necessary. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-01-27 05:14:08 +08:00
if (iter->head >= local_read(&iter->head_page->page->commit)) {
rb_inc_iter(iter);
goto again;
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
event = rb_iter_head_event(iter);
ring_buffer: compressed event header RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes an 'u32' to save the actually length for events which data size > 28. This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA. [ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> LKML-Reference: <49F13189.3090000@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-04-24 11:27:05 +08:00
switch (event->type_len) {
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
case RINGBUF_TYPE_PADDING:
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
if (rb_null_event(event)) {
rb_inc_iter(iter);
goto again;
}
rb_advance_iter(iter);
return event;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
rb_advance_iter(iter);
goto again;
case RINGBUF_TYPE_TIME_STAMP:
/* FIXME: not implemented */
rb_advance_iter(iter);
goto again;
case RINGBUF_TYPE_DATA:
if (ts) {
*ts = iter->read_stamp + event->time_delta;
ring-buffer: add api to allow a tracer to change clock source This patch adds a new function called ring_buffer_set_clock that allows a tracer to assign its own clock source to the buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-18 05:22:06 +08:00
ring_buffer_normalize_time_stamp(buffer,
cpu_buffer->cpu, ts);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
return event;
default:
BUG();
}
return NULL;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
static inline int rb_ok_to_lock(void)
{
/*
* If an NMI die dumps out the content of the ring buffer
* do not grab locks. We also permanently disable the ring
* buffer too. A one time deal is all you get from reading
* the ring buffer from an NMI.
*/
ring-buffer: do not disable ring buffer on oops_in_progress The commit: commit e0fdace10e75dac67d906213b780ff1b1a4cc360 Author: David Miller <davem@davemloft.net> Date: Fri Aug 1 01:11:22 2008 -0700 debug_locks: set oops_in_progress if we will log messages. Otherwise lock debugging messages on runqueue locks can deadlock the system due to the wakeups performed by printk(). Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ingo Molnar <mingo@elte.hu> Will permanently set oops_in_progress on any lockdep failure. When this triggers it will cause any read from the ring buffer to permanently disable the ring buffer (not to mention no locking of printk). This patch removes the check. It keeps the print in NMI which makes sense. This is probably OK, since the ring buffer should not cause something to set oops_in_progress anyway. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-08-06 03:26:37 +08:00
if (likely(!in_nmi()))
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
return 1;
tracing_off_permanent();
return 0;
}
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
/**
* ring_buffer_peek - peek at the next event to be read
* @buffer: The ring buffer to read
* @cpu: The cpu to peak at
* @ts: The timestamp counter of this event.
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
* @lost_events: a variable to store if events were lost (may be NULL)
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
*
* This will return the event that will be read next, but does
* not consume the data.
*/
struct ring_buffer_event *
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
unsigned long *lost_events)
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
struct ring_buffer_event *event;
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
unsigned long flags;
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
int dolock;
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
return NULL;
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
dolock = rb_ok_to_lock();
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
again:
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
local_irq_save(flags);
if (dolock)
spin_lock(&cpu_buffer->reader_lock);
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
ring-buffer: Fix advance of reader in rb_buffer_peek() When calling rb_buffer_peek() from ring_buffer_consume() and a padding event is returned, the function rb_advance_reader() is called twice. This may lead to missing samples or under high workloads to the warning below. This patch fixes this. If a padding event is returned by rb_buffer_peek() it will be consumed by the calling function now. Also, I simplified some code in ring_buffer_consume(). ------------[ cut here ]------------ WARNING: at /dev/shm/.source/linux/kernel/trace/ring_buffer.c:2289 rb_advance_reader+0x2e/0xc5() Hardware name: Anaheim Modules linked in: Pid: 29, comm: events/2 Tainted: G W 2.6.31-rc3-oprofile-x86_64-standard-00059-g5050dc2 #1 Call Trace: [<ffffffff8106776f>] ? rb_advance_reader+0x2e/0xc5 [<ffffffff81039ffe>] warn_slowpath_common+0x77/0x8f [<ffffffff8103a025>] warn_slowpath_null+0xf/0x11 [<ffffffff8106776f>] rb_advance_reader+0x2e/0xc5 [<ffffffff81068bda>] ring_buffer_consume+0xa0/0xd2 [<ffffffff81326933>] op_cpu_buffer_read_entry+0x21/0x9e [<ffffffff810be3af>] ? __find_get_block+0x4b/0x165 [<ffffffff8132749b>] sync_buffer+0xa5/0x401 [<ffffffff810be3af>] ? __find_get_block+0x4b/0x165 [<ffffffff81326c1b>] ? wq_sync_buffer+0x0/0x78 [<ffffffff81326c76>] wq_sync_buffer+0x5b/0x78 [<ffffffff8104aa30>] worker_thread+0x113/0x1ac [<ffffffff8104dd95>] ? autoremove_wake_function+0x0/0x38 [<ffffffff8104a91d>] ? worker_thread+0x0/0x1ac [<ffffffff8104dc9a>] kthread+0x88/0x92 [<ffffffff8100bdba>] child_rip+0xa/0x20 [<ffffffff8104dc12>] ? kthread+0x0/0x92 [<ffffffff8100bdb0>] ? child_rip+0x0/0x20 ---[ end trace f561c0a58fcc89bd ]--- Cc: Steven Rostedt <rostedt@goodmis.org> Cc: <stable@kernel.org> Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-07-31 01:19:18 +08:00
if (event && event->type_len == RINGBUF_TYPE_PADDING)
rb_advance_reader(cpu_buffer);
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
if (dolock)
spin_unlock(&cpu_buffer->reader_lock);
local_irq_restore(flags);
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
ring-buffer: remove unnecessary cpu_relax The loops in the ring buffer that use cpu_relax are not dependent on other CPUs. They simply came across some padding in the ring buffer and are skipping over them. It is a normal loop and does not require a cpu_relax. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:12:13 +08:00
if (event && event->type_len == RINGBUF_TYPE_PADDING)
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
goto again;
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
return event;
}
/**
* ring_buffer_iter_peek - peek at the next event to be read
* @iter: The ring buffer iterator
* @ts: The timestamp counter of this event.
*
* This will return the event that will be read next, but does
* not increment the iterator.
*/
struct ring_buffer_event *
ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
struct ring_buffer_event *event;
unsigned long flags;
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
again:
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
event = rb_iter_peek(iter, ts);
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
ring-buffer: remove unnecessary cpu_relax The loops in the ring buffer that use cpu_relax are not dependent on other CPUs. They simply came across some padding in the ring buffer and are skipping over them. It is a normal loop and does not require a cpu_relax. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:12:13 +08:00
if (event && event->type_len == RINGBUF_TYPE_PADDING)
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
goto again;
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
return event;
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_consume - return an event and consume it
* @buffer: The ring buffer to get the next event from
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
* @cpu: the cpu to read the buffer from
* @ts: a variable to store the timestamp (may be NULL)
* @lost_events: a variable to store if events were lost (may be NULL)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
*
* Returns the next event in the ring buffer, and that event is consumed.
* Meaning, that sequential reads will keep returning a different event,
* and eventually empty the ring buffer if the producer is slower.
*/
struct ring_buffer_event *
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
unsigned long *lost_events)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event = NULL;
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
unsigned long flags;
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
int dolock;
dolock = rb_ok_to_lock();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
again:
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
/* might be called in atomic */
preempt_disable();
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
cpu_buffer = buffer->buffers[cpu];
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
local_irq_save(flags);
if (dolock)
spin_lock(&cpu_buffer->reader_lock);
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
if (event) {
cpu_buffer->lost_events = 0;
ring-buffer: Fix advance of reader in rb_buffer_peek() When calling rb_buffer_peek() from ring_buffer_consume() and a padding event is returned, the function rb_advance_reader() is called twice. This may lead to missing samples or under high workloads to the warning below. This patch fixes this. If a padding event is returned by rb_buffer_peek() it will be consumed by the calling function now. Also, I simplified some code in ring_buffer_consume(). ------------[ cut here ]------------ WARNING: at /dev/shm/.source/linux/kernel/trace/ring_buffer.c:2289 rb_advance_reader+0x2e/0xc5() Hardware name: Anaheim Modules linked in: Pid: 29, comm: events/2 Tainted: G W 2.6.31-rc3-oprofile-x86_64-standard-00059-g5050dc2 #1 Call Trace: [<ffffffff8106776f>] ? rb_advance_reader+0x2e/0xc5 [<ffffffff81039ffe>] warn_slowpath_common+0x77/0x8f [<ffffffff8103a025>] warn_slowpath_null+0xf/0x11 [<ffffffff8106776f>] rb_advance_reader+0x2e/0xc5 [<ffffffff81068bda>] ring_buffer_consume+0xa0/0xd2 [<ffffffff81326933>] op_cpu_buffer_read_entry+0x21/0x9e [<ffffffff810be3af>] ? __find_get_block+0x4b/0x165 [<ffffffff8132749b>] sync_buffer+0xa5/0x401 [<ffffffff810be3af>] ? __find_get_block+0x4b/0x165 [<ffffffff81326c1b>] ? wq_sync_buffer+0x0/0x78 [<ffffffff81326c76>] wq_sync_buffer+0x5b/0x78 [<ffffffff8104aa30>] worker_thread+0x113/0x1ac [<ffffffff8104dd95>] ? autoremove_wake_function+0x0/0x38 [<ffffffff8104a91d>] ? worker_thread+0x0/0x1ac [<ffffffff8104dc9a>] kthread+0x88/0x92 [<ffffffff8100bdba>] child_rip+0xa/0x20 [<ffffffff8104dc12>] ? kthread+0x0/0x92 [<ffffffff8100bdb0>] ? child_rip+0x0/0x20 ---[ end trace f561c0a58fcc89bd ]--- Cc: Steven Rostedt <rostedt@goodmis.org> Cc: <stable@kernel.org> Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-07-31 01:19:18 +08:00
rb_advance_reader(cpu_buffer);
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
}
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
if (dolock)
spin_unlock(&cpu_buffer->reader_lock);
local_irq_restore(flags);
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
out:
preempt_enable();
ring-buffer: remove unnecessary cpu_relax The loops in the ring buffer that use cpu_relax are not dependent on other CPUs. They simply came across some padding in the ring buffer and are skipping over them. It is a normal loop and does not require a cpu_relax. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:12:13 +08:00
if (event && event->type_len == RINGBUF_TYPE_PADDING)
tracing: add ring_buffer_event_discard() to ring buffer This patch overloads RINGBUF_TYPE_PADDING to provide a way to discard events from the ring buffer, for the event-filtering mechanism introduced in a subsequent patch. I did the initial version but thanks to Steven Rostedt for adding the parts that actually made it work. ;-) Signed-off-by: Tom Zanussi <tzanussi@gmail.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-22 16:30:49 +08:00
goto again;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return event;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_consume);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
ring-buffer: Make non-consuming read less expensive with lots of cpus. When performing a non-consuming read, a synchronize_sched() is performed once for every cpu which is actively tracing. This is very expensive, and can make it take several seconds to open up the 'trace' file with lots of cpus. Only one synchronize_sched() call is actually necessary. What is desired is for all cpus to see the disabling state change. So we transform the existing sequence: for_each_cpu() { ring_buffer_read_start(); } where each ring_buffer_start() call performs a synchronize_sched(), into the following: for_each_cpu() { ring_buffer_read_prepare(); } ring_buffer_read_prepare_sync(); for_each_cpu() { ring_buffer_read_start(); } wherein only the single ring_buffer_read_prepare_sync() call needs to do the synchronize_sched(). The first phase, via ring_buffer_read_prepare(), allocates the 'iter' memory and increments ->record_disabled. In the second phase, ring_buffer_read_prepare_sync() makes sure this ->record_disabled state is visible fully to all cpus. And in the final third phase, the ring_buffer_read_start() calls reset the 'iter' objects allocated in the first phase since we now know that none of the cpus are adding trace entries any more. This makes openning the 'trace' file nearly instantaneous on a sparc64 Niagara2 box with 128 cpus tracing. Signed-off-by: David S. Miller <davem@davemloft.net> LKML-Reference: <20100420.154711.11246950.davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-21 06:47:11 +08:00
* ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
* @buffer: The ring buffer to read from
* @cpu: The cpu buffer to iterate over
*
ring-buffer: Make non-consuming read less expensive with lots of cpus. When performing a non-consuming read, a synchronize_sched() is performed once for every cpu which is actively tracing. This is very expensive, and can make it take several seconds to open up the 'trace' file with lots of cpus. Only one synchronize_sched() call is actually necessary. What is desired is for all cpus to see the disabling state change. So we transform the existing sequence: for_each_cpu() { ring_buffer_read_start(); } where each ring_buffer_start() call performs a synchronize_sched(), into the following: for_each_cpu() { ring_buffer_read_prepare(); } ring_buffer_read_prepare_sync(); for_each_cpu() { ring_buffer_read_start(); } wherein only the single ring_buffer_read_prepare_sync() call needs to do the synchronize_sched(). The first phase, via ring_buffer_read_prepare(), allocates the 'iter' memory and increments ->record_disabled. In the second phase, ring_buffer_read_prepare_sync() makes sure this ->record_disabled state is visible fully to all cpus. And in the final third phase, the ring_buffer_read_start() calls reset the 'iter' objects allocated in the first phase since we now know that none of the cpus are adding trace entries any more. This makes openning the 'trace' file nearly instantaneous on a sparc64 Niagara2 box with 128 cpus tracing. Signed-off-by: David S. Miller <davem@davemloft.net> LKML-Reference: <20100420.154711.11246950.davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-21 06:47:11 +08:00
* This performs the initial preparations necessary to iterate
* through the buffer. Memory is allocated, buffer recording
* is disabled, and the iterator pointer is returned to the caller.
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
*
ring-buffer: Make non-consuming read less expensive with lots of cpus. When performing a non-consuming read, a synchronize_sched() is performed once for every cpu which is actively tracing. This is very expensive, and can make it take several seconds to open up the 'trace' file with lots of cpus. Only one synchronize_sched() call is actually necessary. What is desired is for all cpus to see the disabling state change. So we transform the existing sequence: for_each_cpu() { ring_buffer_read_start(); } where each ring_buffer_start() call performs a synchronize_sched(), into the following: for_each_cpu() { ring_buffer_read_prepare(); } ring_buffer_read_prepare_sync(); for_each_cpu() { ring_buffer_read_start(); } wherein only the single ring_buffer_read_prepare_sync() call needs to do the synchronize_sched(). The first phase, via ring_buffer_read_prepare(), allocates the 'iter' memory and increments ->record_disabled. In the second phase, ring_buffer_read_prepare_sync() makes sure this ->record_disabled state is visible fully to all cpus. And in the final third phase, the ring_buffer_read_start() calls reset the 'iter' objects allocated in the first phase since we now know that none of the cpus are adding trace entries any more. This makes openning the 'trace' file nearly instantaneous on a sparc64 Niagara2 box with 128 cpus tracing. Signed-off-by: David S. Miller <davem@davemloft.net> LKML-Reference: <20100420.154711.11246950.davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-21 06:47:11 +08:00
* Disabling buffer recordng prevents the reading from being
* corrupted. This is not a consuming read, so a producer is not
* expected.
*
* After a sequence of ring_buffer_read_prepare calls, the user is
* expected to make at least one call to ring_buffer_prepare_sync.
* Afterwards, ring_buffer_read_start is invoked to get things going
* for real.
*
* This overall must be paired with ring_buffer_finish.
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
*/
struct ring_buffer_iter *
ring-buffer: Make non-consuming read less expensive with lots of cpus. When performing a non-consuming read, a synchronize_sched() is performed once for every cpu which is actively tracing. This is very expensive, and can make it take several seconds to open up the 'trace' file with lots of cpus. Only one synchronize_sched() call is actually necessary. What is desired is for all cpus to see the disabling state change. So we transform the existing sequence: for_each_cpu() { ring_buffer_read_start(); } where each ring_buffer_start() call performs a synchronize_sched(), into the following: for_each_cpu() { ring_buffer_read_prepare(); } ring_buffer_read_prepare_sync(); for_each_cpu() { ring_buffer_read_start(); } wherein only the single ring_buffer_read_prepare_sync() call needs to do the synchronize_sched(). The first phase, via ring_buffer_read_prepare(), allocates the 'iter' memory and increments ->record_disabled. In the second phase, ring_buffer_read_prepare_sync() makes sure this ->record_disabled state is visible fully to all cpus. And in the final third phase, the ring_buffer_read_start() calls reset the 'iter' objects allocated in the first phase since we now know that none of the cpus are adding trace entries any more. This makes openning the 'trace' file nearly instantaneous on a sparc64 Niagara2 box with 128 cpus tracing. Signed-off-by: David S. Miller <davem@davemloft.net> LKML-Reference: <20100420.154711.11246950.davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-21 06:47:11 +08:00
ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
{
struct ring_buffer_per_cpu *cpu_buffer;
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
struct ring_buffer_iter *iter;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
return NULL;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
iter = kmalloc(sizeof(*iter), GFP_KERNEL);
if (!iter)
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
return NULL;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer = buffer->buffers[cpu];
iter->cpu_buffer = cpu_buffer;
atomic_inc(&cpu_buffer->record_disabled);
ring-buffer: Make non-consuming read less expensive with lots of cpus. When performing a non-consuming read, a synchronize_sched() is performed once for every cpu which is actively tracing. This is very expensive, and can make it take several seconds to open up the 'trace' file with lots of cpus. Only one synchronize_sched() call is actually necessary. What is desired is for all cpus to see the disabling state change. So we transform the existing sequence: for_each_cpu() { ring_buffer_read_start(); } where each ring_buffer_start() call performs a synchronize_sched(), into the following: for_each_cpu() { ring_buffer_read_prepare(); } ring_buffer_read_prepare_sync(); for_each_cpu() { ring_buffer_read_start(); } wherein only the single ring_buffer_read_prepare_sync() call needs to do the synchronize_sched(). The first phase, via ring_buffer_read_prepare(), allocates the 'iter' memory and increments ->record_disabled. In the second phase, ring_buffer_read_prepare_sync() makes sure this ->record_disabled state is visible fully to all cpus. And in the final third phase, the ring_buffer_read_start() calls reset the 'iter' objects allocated in the first phase since we now know that none of the cpus are adding trace entries any more. This makes openning the 'trace' file nearly instantaneous on a sparc64 Niagara2 box with 128 cpus tracing. Signed-off-by: David S. Miller <davem@davemloft.net> LKML-Reference: <20100420.154711.11246950.davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-21 06:47:11 +08:00
return iter;
}
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
/**
* ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
*
* All previously invoked ring_buffer_read_prepare calls to prepare
* iterators will be synchronized. Afterwards, read_buffer_read_start
* calls on those iterators are allowed.
*/
void
ring_buffer_read_prepare_sync(void)
{
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
synchronize_sched();
ring-buffer: Make non-consuming read less expensive with lots of cpus. When performing a non-consuming read, a synchronize_sched() is performed once for every cpu which is actively tracing. This is very expensive, and can make it take several seconds to open up the 'trace' file with lots of cpus. Only one synchronize_sched() call is actually necessary. What is desired is for all cpus to see the disabling state change. So we transform the existing sequence: for_each_cpu() { ring_buffer_read_start(); } where each ring_buffer_start() call performs a synchronize_sched(), into the following: for_each_cpu() { ring_buffer_read_prepare(); } ring_buffer_read_prepare_sync(); for_each_cpu() { ring_buffer_read_start(); } wherein only the single ring_buffer_read_prepare_sync() call needs to do the synchronize_sched(). The first phase, via ring_buffer_read_prepare(), allocates the 'iter' memory and increments ->record_disabled. In the second phase, ring_buffer_read_prepare_sync() makes sure this ->record_disabled state is visible fully to all cpus. And in the final third phase, the ring_buffer_read_start() calls reset the 'iter' objects allocated in the first phase since we now know that none of the cpus are adding trace entries any more. This makes openning the 'trace' file nearly instantaneous on a sparc64 Niagara2 box with 128 cpus tracing. Signed-off-by: David S. Miller <davem@davemloft.net> LKML-Reference: <20100420.154711.11246950.davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-21 06:47:11 +08:00
}
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
/**
* ring_buffer_read_start - start a non consuming read of the buffer
* @iter: The iterator returned by ring_buffer_read_prepare
*
* This finalizes the startup of an iteration through the buffer.
* The iterator comes from a call to ring_buffer_read_prepare and
* an intervening ring_buffer_read_prepare_sync must have been
* performed.
*
* Must be paired with ring_buffer_finish.
*/
void
ring_buffer_read_start(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long flags;
if (!iter)
return;
cpu_buffer = iter->cpu_buffer;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
locking: Convert __raw_spin* functions to arch_spin* Name space cleanup. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: linux-arch@vger.kernel.org
2009-12-03 03:01:25 +08:00
arch_spin_lock(&cpu_buffer->lock);
ring-buffer: fix deadlock from reader_lock in read_start Impact: deadlock fix in ring_buffer_read_start The ring_buffer_iter_reset was called from ring_buffer_read_start where both grabbed the reader_lock. This patch separates out the internals of ring_buffer_iter_reset to its own function so that both APIs may grab the reader_lock. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 13:01:26 +08:00
rb_iter_reset(iter);
locking: Convert __raw_spin* functions to arch_spin* Name space cleanup. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: linux-arch@vger.kernel.org
2009-12-03 03:01:25 +08:00
arch_spin_unlock(&cpu_buffer->lock);
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_read_start);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_finish - finish reading the iterator of the buffer
* @iter: The iterator retrieved by ring_buffer_start
*
* This re-enables the recording to the buffer, and frees the
* iterator.
*/
void
ring_buffer_read_finish(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
atomic_dec(&cpu_buffer->record_disabled);
kfree(iter);
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_read - read the next item in the ring buffer by the iterator
* @iter: The ring buffer iterator
* @ts: The time stamp of the event read.
*
* This reads the next event in the ring buffer and increments the iterator.
*/
struct ring_buffer_event *
ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
{
struct ring_buffer_event *event;
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
unsigned long flags;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
ring-buffer: fix ring_buffer_read crossing pages When the ring buffer uses an iterator (static read mode, not on the fly reading), when it crosses a page boundery, it will skip the first entry on the next page. The reason is that the last entry of a page is usually padding if the page is not full. The padding will not be returned to the user. The problem arises on ring_buffer_read because it also increments the iterator. Because both the read and peek use the same rb_iter_peek, the rb_iter_peak will return the padding but also increment to the next item. This is because the ring_buffer_peek will not incerment it itself. The ring_buffer_read will increment it again and then call rb_iter_peek again to get the next item. But that will be the second item, not the first one on the page. The reason this never showed up before, is because the ftrace utility always calls ring_buffer_peek first and only uses ring_buffer_read to increment to the next item. The ring_buffer_peek will always keep the pointer to a valid item and not padding. This just hid the bug. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:02:09 +08:00
again:
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
event = rb_iter_peek(iter, ts);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
if (!event)
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: fix ring_buffer_read crossing pages When the ring buffer uses an iterator (static read mode, not on the fly reading), when it crosses a page boundery, it will skip the first entry on the next page. The reason is that the last entry of a page is usually padding if the page is not full. The padding will not be returned to the user. The problem arises on ring_buffer_read because it also increments the iterator. Because both the read and peek use the same rb_iter_peek, the rb_iter_peak will return the padding but also increment to the next item. This is because the ring_buffer_peek will not incerment it itself. The ring_buffer_read will increment it again and then call rb_iter_peek again to get the next item. But that will be the second item, not the first one on the page. The reason this never showed up before, is because the ftrace utility always calls ring_buffer_peek first and only uses ring_buffer_read to increment to the next item. The ring_buffer_peek will always keep the pointer to a valid item and not padding. This just hid the bug. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-03 22:02:09 +08:00
if (event->type_len == RINGBUF_TYPE_PADDING)
goto again;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
rb_advance_iter(iter);
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
out:
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return event;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_read);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_size - return the size of the ring buffer (in bytes)
* @buffer: The ring buffer.
*/
unsigned long ring_buffer_size(struct ring_buffer *buffer)
{
return BUF_PAGE_SIZE * buffer->pages;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_size);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
static void
rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
{
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_head_page_deactivate(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer->head_page
ring-buffer: make the buffer a true circular link list This patch changes the ring buffer data pages from using a link list head pointer, to making each buffer page point to another buffer page and never back to a "head". This makes the handling of the ring buffer less complex, since the traversing of the ring buffer pages no longer needs to account for the head pointer. This change also is needed to make the ring buffer lockless. [ Changes in version 2: - Added change that Lai Jiangshan mentioned. From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Thu, 11 Jun 2009 11:25:48 +0800 LKML-Reference: <4A30793C.6090208@cn.fujitsu.com> I'm not sure whether these 4 lines: bpage = list_entry(pages.next, struct buffer_page, list); list_del_init(&bpage->list); cpu_buffer->pages = &bpage->list; list_splice(&pages, cpu_buffer->pages); equal to these 2 lines: cpu_buffer->pages = pages.next; list_del(&pages); If there are equivalent, I think the second one are simpler. It may be not a really necessarily cleanup. What I asked is: if there are equivalent, could you use these two line: cpu_buffer->pages = pages.next; list_del(&pages); ] [ Impact: simplify the ring buffer to help make it lockless ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-31 03:32:01 +08:00
= list_entry(cpu_buffer->pages, struct buffer_page, list);
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
local_set(&cpu_buffer->head_page->write, 0);
ring-buffer: record page entries in buffer page descriptor Currently, when the ring buffer writer overflows the buffer and must write over non consumed data, we increment the overrun counter by reading the entries on the page we are about to overwrite. This reads the entries one by one. This is not very effecient. This patch adds another entry counter into each buffer page descriptor that keeps track of the number of entries on the page. Now on overwrite, the overrun counter simply needs to add the number of entries that is on the page it is about to overwrite. [ Impact: speed up of ring buffer in overwrite mode ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-02 06:44:45 +08:00
local_set(&cpu_buffer->head_page->entries, 0);
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
local_set(&cpu_buffer->head_page->page->commit, 0);
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
ring-buffer: move page indexes into page headers Remove the global head and tail indexes and move them into the page header. Each page will now keep track of where the last write and read was made. We also rename the head and tail to read and write for better clarification. This patch is needed for future enhancements to move the ring buffer to a lockless solution. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:58 +08:00
cpu_buffer->head_page->read = 0;
ring-buffer: make reentrant This patch replaces the local_irq_save/restore with preempt_disable/ enable. This allows for interrupts to enter while recording. To write to the ring buffer, you must reserve data, and then commit it. During this time, an interrupt may call a trace function that will also record into the buffer before the commit is made. The interrupt will reserve its entry after the first entry, even though the first entry did not finish yet. The time stamp delta of the interrupt entry will be zero, since in the view of the trace, the interrupt happened during the first field anyway. Locking still takes place when the tail/write moves from one page to the next. The reader always takes the locks. A new page pointer is added, called the commit. The write/tail will always point to the end of all entries. The commit field will point to the last committed entry. Only this commit entry may update the write time stamp. The reader can only go up to the commit. It cannot go past it. If a lot of interrupts come in during a commit that fills up the buffer, and it happens to make it all the way around the buffer back to the commit, then a warning is printed and new events will be dropped. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:59 +08:00
cpu_buffer->tail_page = cpu_buffer->head_page;
cpu_buffer->commit_page = cpu_buffer->head_page;
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
local_set(&cpu_buffer->reader_page->write, 0);
ring-buffer: record page entries in buffer page descriptor Currently, when the ring buffer writer overflows the buffer and must write over non consumed data, we increment the overrun counter by reading the entries on the page we are about to overwrite. This reads the entries one by one. This is not very effecient. This patch adds another entry counter into each buffer page descriptor that keeps track of the number of entries on the page. Now on overwrite, the overrun counter simply needs to add the number of entries that is on the page it is about to overwrite. [ Impact: speed up of ring buffer in overwrite mode ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-02 06:44:45 +08:00
local_set(&cpu_buffer->reader_page->entries, 0);
ring-buffer: move some metadata into buffer page Impact: get ready for splice changes This patch moves the commit and timestamp into the beginning of each data page of the buffer. This change will allow the page to be moved to another location (disk, network, etc) and still have information in the page to be able to read it. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:06 +08:00
local_set(&cpu_buffer->reader_page->page->commit, 0);
ring-buffer: move page indexes into page headers Remove the global head and tail indexes and move them into the page header. Each page will now keep track of where the last write and read was made. We also rename the head and tail to read and write for better clarification. This patch is needed for future enhancements to move the ring buffer to a lockless solution. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-04 14:00:58 +08:00
cpu_buffer->reader_page->read = 0;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
local_set(&cpu_buffer->commit_overrun, 0);
local_set(&cpu_buffer->overrun, 0);
ring-buffer: convert cpu buffer entries to local_t The entries counter in cpu buffer is not atomic. It can be updated by other interrupts or from another CPU (readers). But making entries into "atomic_t" causes an atomic operation that can hurt performance. Instead we convert it to a local_t that will increment a counter with a local CPU atomic operation (if the arch supports it). Instead of fighting with readers and overwrites that decrement the counter, I added a "read" counter. Every time a reader reads an entry it is incremented. We already have a overrun counter and with that, the entries counter and the read counter, we can calculate the total number of entries in the buffer with: (entries - overrun) - read As long as the total number of entries in the ring buffer is less than the word size, this will work. But since the entries counter was previously a long, this is no different than what we had before. Thanks to Andrew Morton for pointing out in the first version that atomic_t does not replace unsigned long. I switched to atomic_long_t even though it is signed. A negative count is most likely a bug. [ Impact: keep accurate count of cpu buffer entries ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-01 08:49:44 +08:00
local_set(&cpu_buffer->entries, 0);
ring-buffer: use commit counters for commit pointer accounting The ring buffer is made up of three sets of pointers. The head page pointer, which points to the next page for the reader to get. The commit pointer and commit index, which points to the page and index of the last committed write respectively. The tail pointer and tail index, which points to the page and the index of the last reserved data respectively (non committed). The commit pointer is only moved forward by the outer most writer. If a nested writer comes in, it will not move the pointer forward. The current implementation has a flaw. It assumes that the outer most writer successfully reserved data. There's a small race window where the outer most writer could find the tail pointer, but a nested writer could come in (via interrupt) and move the tail forward, and even the commit forward. The outer writer would not realized the commit moved forward and the accounting will break. This patch changes the design to use counters in the per cpu buffers to keep track of commits. The counters are incremented at the start of the commit, and decremented at the end. If the end commit counter is 1, then it moves the commit pointers. A loop is made to check for races between checking and moving the commit pointers. Only the outer commit should move the pointers anyway. The test of knowing if a reserve is equal to the last commit update is still needed to know for time keeping. The time code is much less racey than the commit updates. This change not only solves the mentioned race, but also makes the code simpler. [ Impact: fix commit race and simplify code ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 00:37:57 +08:00
local_set(&cpu_buffer->committing, 0);
local_set(&cpu_buffer->commits, 0);
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
cpu_buffer->read = 0;
ring-buffer: reset timestamps when ring buffer is reset Impact: fix bad times of recent resets The ring buffer needs to reset its timestamps when reseting of the buffer, otherwise the timestamps are stale and might be used to calculate times in the buffer causing funny timestamps to appear. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-22 07:45:57 +08:00
cpu_buffer->write_stamp = 0;
cpu_buffer->read_stamp = 0;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
cpu_buffer->lost_events = 0;
cpu_buffer->last_overrun = 0;
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
rb_head_page_activate(cpu_buffer);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
/**
* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
* @buffer: The ring buffer to reset a per cpu buffer of
* @cpu: The CPU buffer to be reset
*/
void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
unsigned long flags;
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
return;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: disable writers when resetting buffers As a precaution, it is best to disable writing to the ring buffers when reseting them. [ Impact: prevent weird things if write happens during reset ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-02 08:26:54 +08:00
atomic_inc(&cpu_buffer->record_disabled);
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
ring-buffer: do not reset while in a commit The callers of reset must ensure that no commit can be taking place at the time of the reset. If it does then we may corrupt the ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-02 21:59:48 +08:00
if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
goto out;
locking: Convert __raw_spin* functions to arch_spin* Name space cleanup. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: linux-arch@vger.kernel.org
2009-12-03 03:01:25 +08:00
arch_spin_lock(&cpu_buffer->lock);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
rb_reset_cpu(cpu_buffer);
locking: Convert __raw_spin* functions to arch_spin* Name space cleanup. No functional change. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: linux-arch@vger.kernel.org
2009-12-03 03:01:25 +08:00
arch_spin_unlock(&cpu_buffer->lock);
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
ring-buffer: do not reset while in a commit The callers of reset must ensure that no commit can be taking place at the time of the reset. If it does then we may corrupt the ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-02 21:59:48 +08:00
out:
ring-buffer: add reader lock Impact: serialize reader accesses to individual CPU ring buffers The code in the ring buffer expects only one reader at a time, but currently it puts that requirement on the caller. This is not strong enough, and this patch adds a "reader_lock" that serializes the access to the reader API of the ring buffer. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-12 01:47:44 +08:00
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
ring-buffer: disable writers when resetting buffers As a precaution, it is best to disable writing to the ring buffers when reseting them. [ Impact: prevent weird things if write happens during reset ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-02 08:26:54 +08:00
atomic_dec(&cpu_buffer->record_disabled);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_reset - reset a ring buffer
* @buffer: The ring buffer to reset all cpu buffers
*/
void ring_buffer_reset(struct ring_buffer *buffer)
{
int cpu;
for_each_buffer_cpu(buffer, cpu)
ring_buffer: implement new locking The old "lock always" scheme had issues with lockdep, and was not very efficient anyways. This patch does a new design to be partially lockless on writes. Writes will add new entries to the per cpu pages by simply disabling interrupts. When a write needs to go to another page than it will grab the lock. A new "read page" has been added so that the reader can pull out a page from the ring buffer to read without worrying about the writer writing over it. This allows us to not take the lock for all reads. The lock is now only taken when a read needs to go to a new page. This is far from lockless, and interrupts still need to be disabled, but it is a step towards a more lockless solution, and it also solves a lot of the issues that were noticed by the first conversion of ftrace to the ring buffers. Note: the ring_buffer_{un}lock API has been removed. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-01 12:29:53 +08:00
ring_buffer_reset_cpu(buffer, cpu);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_reset);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* rind_buffer_empty - is the ring buffer empty?
* @buffer: The ring buffer to test
*/
int ring_buffer_empty(struct ring_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
ring-buffer: add locks around rb_per_cpu_empty The checking of whether the buffer is empty or not needs to be serialized among the readers. Add the reader spin lock around it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 12:39:43 +08:00
unsigned long flags;
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
int dolock;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
int cpu;
ring-buffer: add locks around rb_per_cpu_empty The checking of whether the buffer is empty or not needs to be serialized among the readers. Add the reader spin lock around it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 12:39:43 +08:00
int ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
dolock = rb_ok_to_lock();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/* yes this is racy, but if you don't like the race, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
local_irq_save(flags);
if (dolock)
spin_lock(&cpu_buffer->reader_lock);
ring-buffer: add locks around rb_per_cpu_empty The checking of whether the buffer is empty or not needs to be serialized among the readers. Add the reader spin lock around it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 12:39:43 +08:00
ret = rb_per_cpu_empty(cpu_buffer);
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
if (dolock)
spin_unlock(&cpu_buffer->reader_lock);
local_irq_restore(flags);
ring-buffer: add locks around rb_per_cpu_empty The checking of whether the buffer is empty or not needs to be serialized among the readers. Add the reader spin lock around it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 12:39:43 +08:00
if (!ret)
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return 0;
}
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
return 1;
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_empty);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
* @buffer: The ring buffer
* @cpu: The CPU buffer to test
*/
int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
ring-buffer: add locks around rb_per_cpu_empty The checking of whether the buffer is empty or not needs to be serialized among the readers. Add the reader spin lock around it. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 12:39:43 +08:00
unsigned long flags;
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
int dolock;
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
int ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: remove unneeded get_online_cpus Impact: speed up and remove possible races The get_online_cpus was added to the ring buffer because the original design would free the ring buffer on a CPU that was being taken off line. The final design kept the ring buffer around even when the CPU was taken off line. This is to allow a user to still read the information on that ring buffer. Most of the get_online_cpus are no longer needed since the ring buffer will not disappear from the use cases. Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-13 01:13:49 +08:00
return 1;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
dolock = rb_ok_to_lock();
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer = buffer->buffers[cpu];
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
local_irq_save(flags);
if (dolock)
spin_lock(&cpu_buffer->reader_lock);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
ret = rb_per_cpu_empty(cpu_buffer);
ring-buffer: do not grab locks in nmi If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it will need to read from the ring buffer. But the read side of the ring buffer still takes locks. This patch adds a check on the read side that if it is in an NMI, then it will disable the ring buffer and not take any locks. Reads can still happen on a disabled ring buffer. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-17 09:22:48 +08:00
if (dolock)
spin_unlock(&cpu_buffer->reader_lock);
local_irq_restore(flags);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
return ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: only enable ring_buffer_swap_cpu when needed Since the ability to swap the cpu buffers adds a small overhead to the recording of a trace, we only want to add it when needed. Only the irqsoff and preemptoff tracers use this feature, and both are not recommended for production kernels. This patch disables its use when neither irqsoff nor preemptoff is configured. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-05 02:24:40 +08:00
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/**
* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
* @buffer_a: One buffer to swap with
* @buffer_b: The other buffer to swap with
*
* This function is useful for tracers that want to take a "snapshot"
* of a CPU buffer and has another back up buffer lying around.
* it is expected that the tracer handles the cpu buffer not being
* used at the moment.
*/
int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
struct ring_buffer *buffer_b, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer_a;
struct ring_buffer_per_cpu *cpu_buffer_b;
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
int ret = -EINVAL;
cpumask: convert kernel trace functions Impact: Reduce future memory usage, use new cpumask API. (Eventually, cpumask_var_t will be allocated based on nr_cpu_ids, not NR_CPUS). Convert kernel trace functions to use struct cpumask API: 1) Use cpumask_copy/cpumask_test_cpu/for_each_cpu. 2) Use cpumask_var_t and alloc_cpumask_var/free_cpumask_var everywhere. 3) Use on_each_cpu instead of playing with current->cpus_allowed. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Mike Travis <travis@sgi.com> Acked-by: Steven Rostedt <rostedt@goodmis.org>
2009-01-01 07:42:22 +08:00
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
!cpumask_test_cpu(cpu, buffer_b->cpumask))
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/* At least make sure the two buffers are somewhat the same */
tracing/ring-buffer: remove unused ring_buffer size Impact: remove dead code struct ring_buffer.size is not set after ring_buffer is initialized or resized. it is always 0. we can use "buffer->pages * PAGE_SIZE" to get ring_buffer's size Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-17 17:48:23 +08:00
if (buffer_a->pages != buffer_b->pages)
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
ret = -EAGAIN;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: do not swap if recording is disabled If the ring buffer recording has been disabled. Do not let swapping of ring buffers occur. Simply return -EAGAIN. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-22 04:24:56 +08:00
if (ring_buffer_flags != RB_BUFFERS_ON)
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
ring-buffer: do not swap if recording is disabled If the ring buffer recording has been disabled. Do not let swapping of ring buffers occur. Simply return -EAGAIN. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-22 04:24:56 +08:00
if (atomic_read(&buffer_a->record_disabled))
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
ring-buffer: do not swap if recording is disabled If the ring buffer recording has been disabled. Do not let swapping of ring buffers occur. Simply return -EAGAIN. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-22 04:24:56 +08:00
if (atomic_read(&buffer_b->record_disabled))
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
ring-buffer: do not swap if recording is disabled If the ring buffer recording has been disabled. Do not let swapping of ring buffers occur. Simply return -EAGAIN. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-22 04:24:56 +08:00
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
cpu_buffer_a = buffer_a->buffers[cpu];
cpu_buffer_b = buffer_b->buffers[cpu];
ring-buffer: do not swap if recording is disabled If the ring buffer recording has been disabled. Do not let swapping of ring buffers occur. Simply return -EAGAIN. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-22 04:24:56 +08:00
if (atomic_read(&cpu_buffer_a->record_disabled))
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
ring-buffer: do not swap if recording is disabled If the ring buffer recording has been disabled. Do not let swapping of ring buffers occur. Simply return -EAGAIN. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-22 04:24:56 +08:00
if (atomic_read(&cpu_buffer_b->record_disabled))
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
ring-buffer: do not swap if recording is disabled If the ring buffer recording has been disabled. Do not let swapping of ring buffers occur. Simply return -EAGAIN. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-22 04:24:56 +08:00
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
/*
* We can't do a synchronize_sched here because this
* function can be called in atomic context.
* Normally this will be called from the same CPU as cpu.
* If not it's up to the caller to protect this.
*/
atomic_inc(&cpu_buffer_a->record_disabled);
atomic_inc(&cpu_buffer_b->record_disabled);
ring-buffer: do not swap buffers during a commit If a commit is taking place on a CPU ring buffer, do not allow it to be swapped. Return -EBUSY when this is detected instead. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-02 22:56:15 +08:00
ret = -EBUSY;
if (local_read(&cpu_buffer_a->committing))
goto out_dec;
if (local_read(&cpu_buffer_b->committing))
goto out_dec;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
buffer_a->buffers[cpu] = cpu_buffer_b;
buffer_b->buffers[cpu] = cpu_buffer_a;
cpu_buffer_b->buffer = buffer_a;
cpu_buffer_a->buffer = buffer_b;
ring-buffer: do not swap buffers during a commit If a commit is taking place on a CPU ring buffer, do not allow it to be swapped. Return -EBUSY when this is detected instead. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-02 22:56:15 +08:00
ret = 0;
out_dec:
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
atomic_dec(&cpu_buffer_a->record_disabled);
atomic_dec(&cpu_buffer_b->record_disabled);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
out:
return ret;
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
}
ring_buffer: adding EXPORT_SYMBOLs I added EXPORT_SYMBOL_GPLs for all functions part of the API (ring_buffer.h). This is required since oprofile is using the ring buffer and the compilation as modules would fail otherwise. Signed-off-by: Robert Richter <robert.richter@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-11 23:49:22 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
ring-buffer: only enable ring_buffer_swap_cpu when needed Since the ability to swap the cpu buffers adds a small overhead to the recording of a trace, we only want to add it when needed. Only the irqsoff and preemptoff tracers use this feature, and both are not recommended for production kernels. This patch disables its use when neither irqsoff nor preemptoff is configured. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-09-05 02:24:40 +08:00
#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
tracing: unified trace buffer This is a unified tracing buffer that implements a ring buffer that hopefully everyone will eventually be able to use. The events recorded into the buffer have the following structure: struct ring_buffer_event { u32 type:2, len:3, time_delta:27; u32 array[]; }; The minimum size of an event is 8 bytes. All events are 4 byte aligned inside the buffer. There are 4 types (all internal use for the ring buffer, only the data type is exported to the interface users). RINGBUF_TYPE_PADDING: this type is used to note extra space at the end of a buffer page. RINGBUF_TYPE_TIME_EXTENT: This type is used when the time between events is greater than the 27 bit delta can hold. We add another 32 bits, and record that in its own event (8 byte size). RINGBUF_TYPE_TIME_STAMP: (Not implemented yet). This will hold data to help keep the buffer timestamps in sync. RINGBUF_TYPE_DATA: The event actually holds user data. The "len" field is only three bits. Since the data must be 4 byte aligned, this field is shifted left by 2, giving a max length of 28 bytes. If the data load is greater than 28 bytes, the first array field holds the full length of the data load and the len field is set to zero. Example, data size of 7 bytes: type = RINGBUF_TYPE_DATA len = 2 time_delta: <time-stamp> - <prev_event-time-stamp> array[0..1]: <7 bytes of data> <1 byte empty> This event is saved in 12 bytes of the buffer. An event with 82 bytes of data: type = RINGBUF_TYPE_DATA len = 0 time_delta: <time-stamp> - <prev_event-time-stamp> array[0]: 84 (Note the alignment) array[1..14]: <82 bytes of data> <2 bytes empty> The above event is saved in 92 bytes (if my math is correct). 82 bytes of data, 2 bytes empty, 4 byte header, 4 byte length. Do not reference the above event struct directly. Use the following functions to gain access to the event table, since the ring_buffer_event structure may change in the future. ring_buffer_event_length(event): get the length of the event. This is the size of the memory used to record this event, and not the size of the data pay load. ring_buffer_time_delta(event): get the time delta of the event This returns the delta time stamp since the last event. Note: Even though this is in the header, there should be no reason to access this directly, accept for debugging. ring_buffer_event_data(event): get the data from the event This is the function to use to get the actual data from the event. Note, it is only a pointer to the data inside the buffer. This data must be copied to another location otherwise you risk it being written over in the buffer. ring_buffer_lock: A way to lock the entire buffer. ring_buffer_unlock: unlock the buffer. ring_buffer_alloc: create a new ring buffer. Can choose between overwrite or consumer/producer mode. Overwrite will overwrite old data, where as consumer producer will throw away new data if the consumer catches up with the producer. The consumer/producer is the default. ring_buffer_free: free the ring buffer. ring_buffer_resize: resize the buffer. Changes the size of each cpu buffer. Note, it is up to the caller to provide that the buffer is not being used while this is happening. This requirement may go away but do not count on it. ring_buffer_lock_reserve: locks the ring buffer and allocates an entry on the buffer to write to. ring_buffer_unlock_commit: unlocks the ring buffer and commits it to the buffer. ring_buffer_write: writes some data into the ring buffer. ring_buffer_peek: Look at a next item in the cpu buffer. ring_buffer_consume: get the next item in the cpu buffer and consume it. That is, this function increments the head pointer. ring_buffer_read_start: Start an iterator of a cpu buffer. For now, this disables the cpu buffer, until you issue a finish. This is just because we do not want the iterator to be overwritten. This restriction may change in the future. But note, this is used for static reading of a buffer which is usually done "after" a trace. Live readings would want to use the ring_buffer_consume above, which will not disable the ring buffer. ring_buffer_read_finish: Finishes the read iterator and reenables the ring buffer. ring_buffer_iter_peek: Look at the next item in the cpu iterator. ring_buffer_read: Read the iterator and increment it. ring_buffer_iter_reset: Reset the iterator to point to the beginning of the cpu buffer. ring_buffer_iter_empty: Returns true if the iterator is at the end of the cpu buffer. ring_buffer_size: returns the size in bytes of each cpu buffer. Note, the real size is this times the number of CPUs. ring_buffer_reset_cpu: Sets the cpu buffer to empty ring_buffer_reset: sets all cpu buffers to empty ring_buffer_swap_cpu: swaps a cpu buffer from one buffer with a cpu buffer of another buffer. This is handy when you want to take a snap shot of a running trace on just one cpu. Having a backup buffer, to swap with facilitates this. Ftrace max latencies use this. ring_buffer_empty: Returns true if the ring buffer is empty. ring_buffer_empty_cpu: Returns true if the cpu buffer is empty. ring_buffer_record_disable: disable all cpu buffers (read only) ring_buffer_record_disable_cpu: disable a single cpu buffer (read only) ring_buffer_record_enable: enable all cpu buffers. ring_buffer_record_enabl_cpu: enable a single cpu buffer. ring_buffer_entries: The number of entries in a ring buffer. ring_buffer_overruns: The number of entries removed due to writing wrap. ring_buffer_time_stamp: Get the time stamp used by the ring buffer ring_buffer_normalize_time_stamp: normalize the ring buffer time stamp into nanosecs. I still need to implement the GTOD feature. But we need support from the cpu frequency infrastructure. But this can be done at a later time without affecting the ring buffer interface. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-30 11:02:38 +08:00
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
/**
* ring_buffer_alloc_read_page - allocate a page to read from buffer
* @buffer: the buffer to allocate for.
*
* This function is used in conjunction with ring_buffer_read_page.
* When reading a full page from the ring buffer, these functions
* can be used to speed up the process. The calling function should
* allocate a few pages first with this function. Then when it
* needs to get pages from the ring buffer, it passes the result
* of this function into ring_buffer_read_page, which will swap
* the page that was allocated, with the read page of the buffer.
*
* Returns:
* The page allocated, or NULL on error.
*/
void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
{
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
struct buffer_data_page *bpage;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
unsigned long addr;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
addr = __get_free_page(GFP_KERNEL);
if (!addr)
return NULL;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage = (void *)addr;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
rb_init_page(bpage);
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
return bpage;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
}
ring-buffer: export symbols I'm adding a module to do a series of tests on the ring buffer as well as benchmarks. This module needs to have more of the ring buffer API exported. There's nothing wrong with reading the ring buffer from a module. [ Impact: allow modules to read pages from the ring buffer ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-05 13:15:24 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
/**
* ring_buffer_free_read_page - free an allocated read page
* @buffer: the buffer the page was allocate for
* @data: the page to free
*
* Free a page allocated from ring_buffer_alloc_read_page.
*/
void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
{
free_page((unsigned long)data);
}
ring-buffer: export symbols I'm adding a module to do a series of tests on the ring buffer as well as benchmarks. This module needs to have more of the ring buffer API exported. There's nothing wrong with reading the ring buffer from a module. [ Impact: allow modules to read pages from the ring buffer ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-05 13:15:24 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
/**
* ring_buffer_read_page - extract a page from the ring buffer
* @buffer: buffer to extract from
* @data_page: the page to use allocated from ring_buffer_alloc_read_page
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
* @len: amount to extract
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
* @cpu: the cpu of the buffer to extract
* @full: should the extraction only happen when the page is full.
*
* This function will pull out a page from the ring buffer and consume it.
* @data_page must be the address of the variable that was returned
* from ring_buffer_alloc_read_page. This is because the page might be used
* to swap with a page in the ring buffer.
*
* for example:
ring_buffer: fix typing mistake Impact: Fix bug I found several very very curious line. It's so curious that it may be brought by typing mistake. When (cpu_buffer->reader_page == cpu_buffer->commit_page): 1) We haven't copied it for bpage is changed: bpage = cpu_buffer->reader_page->page; memcpy(bpage->data, cpu_buffer->reader_page->page->data + read ... ) 2) We need update cpu_buffer->reader_page->read, but "cpu_buffer->reader_page += read;" is not right. [ This bug was a typo. The commit->reader_page is a page pointer and not an index into the page. The line should have been commit->reader_page->read += read. The other changes by Lai are nice clean ups to the code. - SDR ] Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-09 14:21:14 +08:00
* rpage = ring_buffer_alloc_read_page(buffer);
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
* if (!rpage)
* return error;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
* ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
ring_buffer: fix ring_buffer_read_page() Impact: change API and init bpage when copy ring_buffer_read_page()/rb_remove_entries() may be called for a partially consumed page. Add a parameter for rb_remove_entries() and make it update cpu_buffer->entries correctly for partially consumed pages. ring_buffer_read_page() now returns the offset to the next event. Init the bpage's time_stamp when return value is 0. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-09 14:21:17 +08:00
* if (ret >= 0)
* process_page(rpage, ret);
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
*
* When @full is set, the function will not return true unless
* the writer is off the reader page.
*
* Note: it is up to the calling functions to handle sleeps and wakeups.
* The ring buffer can be used anywhere in the kernel and can not
* blindly call wake_up. The layer that uses the ring buffer must be
* responsible for that.
*
* Returns:
ring_buffer: fix ring_buffer_read_page() Impact: change API and init bpage when copy ring_buffer_read_page()/rb_remove_entries() may be called for a partially consumed page. Add a parameter for rb_remove_entries() and make it update cpu_buffer->entries correctly for partially consumed pages. ring_buffer_read_page() now returns the offset to the next event. Init the bpage's time_stamp when return value is 0. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-09 14:21:17 +08:00
* >=0 if data has been transferred, returns the offset of consumed data.
* <0 if no data has been transferred.
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
*/
int ring_buffer_read_page(struct ring_buffer *buffer,
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
void **data_page, size_t len, int cpu, int full)
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
struct ring_buffer_event *event;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
struct buffer_data_page *bpage;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
struct buffer_page *reader;
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
unsigned long missed_events;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
unsigned long flags;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
unsigned int commit;
ring_buffer: fix ring_buffer_read_page() Impact: change API and init bpage when copy ring_buffer_read_page()/rb_remove_entries() may be called for a partially consumed page. Add a parameter for rb_remove_entries() and make it update cpu_buffer->entries correctly for partially consumed pages. ring_buffer_read_page() now returns the offset to the next event. Init the bpage's time_stamp when return value is 0. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-09 14:21:17 +08:00
unsigned int read;
ring-buffer: fix timestamp in partial ring_buffer_page_read If a partial ring_buffer_page_read happens, then some of the incremental timestamps may be lost. This patch writes the recent timestamp into the page that is passed back to the caller. A partial ring_buffer_page_read is where the full page would not be written back to the user, and instead, just part of the page is copied to the user. A full page would be a page swap with the ring buffer and the timestamps would be correct. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 12:52:42 +08:00
u64 save_timestamp;
ring_buffer: fix ring_buffer_read_page() Impact: change API and init bpage when copy ring_buffer_read_page()/rb_remove_entries() may be called for a partially consumed page. Add a parameter for rb_remove_entries() and make it update cpu_buffer->entries correctly for partially consumed pages. ring_buffer_read_page() now returns the offset to the next event. Init the bpage's time_stamp when return value is 0. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-09 14:21:17 +08:00
int ret = -1;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
if (!cpumask_test_cpu(cpu, buffer->cpumask))
goto out;
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
/*
* If len is not big enough to hold the page header, then
* we can not copy anything.
*/
if (len <= BUF_PAGE_HDR_SIZE)
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
len -= BUF_PAGE_HDR_SIZE;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
if (!data_page)
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
bpage = *data_page;
if (!bpage)
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
reader = rb_get_reader_page(cpu_buffer);
if (!reader)
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out_unlock;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
event = rb_reader_event(cpu_buffer);
read = reader->read;
commit = rb_page_commit(reader);
ring_buffer: fix ring_buffer_read_page() Impact: change API and init bpage when copy ring_buffer_read_page()/rb_remove_entries() may be called for a partially consumed page. Add a parameter for rb_remove_entries() and make it update cpu_buffer->entries correctly for partially consumed pages. ring_buffer_read_page() now returns the offset to the next event. Init the bpage's time_stamp when return value is 0. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-09 14:21:17 +08:00
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
/* Check if any events were dropped */
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
missed_events = cpu_buffer->lost_events;
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
/*
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
* If this page has been partially read or
* if len is not big enough to read the rest of the page or
* a writer is still on the page, then
* we must copy the data from the page to the buffer.
* Otherwise, we can simply swap the page with the one passed in.
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
*/
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
if (read || (len < (commit - read)) ||
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
cpu_buffer->reader_page == cpu_buffer->commit_page) {
ring_buffer: fix ring_buffer_read_page() Impact: change API and init bpage when copy ring_buffer_read_page()/rb_remove_entries() may be called for a partially consumed page. Add a parameter for rb_remove_entries() and make it update cpu_buffer->entries correctly for partially consumed pages. ring_buffer_read_page() now returns the offset to the next event. Init the bpage's time_stamp when return value is 0. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-09 14:21:17 +08:00
struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
unsigned int rpos = read;
unsigned int pos = 0;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
unsigned int size;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
if (full)
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out_unlock;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
if (len > (commit - read))
len = (commit - read);
size = rb_event_length(event);
if (len < size)
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
goto out_unlock;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
ring-buffer: fix timestamp in partial ring_buffer_page_read If a partial ring_buffer_page_read happens, then some of the incremental timestamps may be lost. This patch writes the recent timestamp into the page that is passed back to the caller. A partial ring_buffer_page_read is where the full page would not be written back to the user, and instead, just part of the page is copied to the user. A full page would be a page swap with the ring buffer and the timestamps would be correct. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 12:52:42 +08:00
/* save the current timestamp, since the user will need it */
save_timestamp = cpu_buffer->read_stamp;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
/* Need to copy one event at a time */
do {
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
memcpy(bpage->data + pos, rpage->data + rpos, size);
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
len -= size;
rb_advance_reader(cpu_buffer);
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
rpos = reader->read;
pos += size;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
tracing: Fix ring_buffer_read_page reading out of page boundary With the configuration: CONFIG_DEBUG_PAGEALLOC=y and Shaohua's patch: [PATCH]x86: make spurious_fault check correct pte bit Function call graph trace with the following will trigger a page fault. # cd /sys/kernel/debug/tracing/ # echo function_graph > current_tracer # cat per_cpu/cpu1/trace_pipe_raw > /dev/null BUG: unable to handle kernel paging request at ffff880006e99000 IP: [<ffffffff81085572>] rb_event_length+0x1/0x3f PGD 1b19063 PUD 1b1d063 PMD 3f067 PTE 6e99160 Oops: 0000 [#1] SMP DEBUG_PAGEALLOC last sysfs file: /sys/devices/virtual/net/lo/operstate CPU 1 Modules linked in: Pid: 1982, comm: cat Not tainted 2.6.35-rc6-aes+ #300 /Bochs RIP: 0010:[<ffffffff81085572>] [<ffffffff81085572>] rb_event_length+0x1/0x3f RSP: 0018:ffff880006475e38 EFLAGS: 00010006 RAX: 0000000000000ff0 RBX: ffff88000786c630 RCX: 000000000000001d RDX: ffff880006e98000 RSI: 0000000000000ff0 RDI: ffff880006e99000 RBP: ffff880006475eb8 R08: 000000145d7008bd R09: 0000000000000000 R10: 0000000000008000 R11: ffffffff815d9336 R12: ffff880006d08000 R13: ffff880006e605d8 R14: 0000000000000000 R15: 0000000000000018 FS: 00007f2b83e456f0(0000) GS:ffff880002100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: ffff880006e99000 CR3: 00000000064a8000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process cat (pid: 1982, threadinfo ffff880006474000, task ffff880006e40770) Stack: ffff880006475eb8 ffffffff8108730f 0000000000000ff0 000000145d7008bd <0> ffff880006e98010 ffff880006d08010 0000000000000296 ffff88000786c640 <0> ffffffff81002956 0000000000000000 ffff8800071f4680 ffff8800071f4680 Call Trace: [<ffffffff8108730f>] ? ring_buffer_read_page+0x15a/0x24a [<ffffffff81002956>] ? return_to_handler+0x15/0x2f [<ffffffff8108a575>] tracing_buffers_read+0xb9/0x164 [<ffffffff810debfe>] vfs_read+0xaf/0x150 [<ffffffff81002941>] return_to_handler+0x0/0x2f [<ffffffff810248b0>] __bad_area_nosemaphore+0x17e/0x1a1 [<ffffffff81002941>] return_to_handler+0x0/0x2f [<ffffffff810248e6>] bad_area_nosemaphore+0x13/0x15 Code: 80 25 b2 16 b3 00 fe c9 c3 55 48 89 e5 f0 80 0d a4 16 b3 00 02 c9 c3 55 31 c0 48 89 e5 48 83 3d 94 16 b3 00 01 c9 0f 94 c0 c3 55 <8a> 0f 48 89 e5 83 e1 1f b8 08 00 00 00 0f b6 d1 83 fa 1e 74 27 RIP [<ffffffff81085572>] rb_event_length+0x1/0x3f RSP <ffff880006475e38> CR2: ffff880006e99000 ---[ end trace a6877bb92ccb36bb ]--- The root cause is that ring_buffer_read_page() may read out of page boundary, because the boundary checking is done after reading. This is fixed via doing boundary checking before reading. Reported-by: Shaohua Li <shaohua.li@intel.com> Cc: <stable@kernel.org> Signed-off-by: Huang Ying <ying.huang@intel.com> LKML-Reference: <1280297641.2771.307.camel@yhuang-dev> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-07-28 14:14:01 +08:00
if (rpos >= commit)
break;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
event = rb_reader_event(cpu_buffer);
size = rb_event_length(event);
} while (len > size);
ring_buffer: fix ring_buffer_read_page() Impact: change API and init bpage when copy ring_buffer_read_page()/rb_remove_entries() may be called for a partially consumed page. Add a parameter for rb_remove_entries() and make it update cpu_buffer->entries correctly for partially consumed pages. ring_buffer_read_page() now returns the offset to the next event. Init the bpage's time_stamp when return value is 0. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-09 14:21:17 +08:00
/* update bpage */
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
local_set(&bpage->commit, pos);
ring-buffer: fix timestamp in partial ring_buffer_page_read If a partial ring_buffer_page_read happens, then some of the incremental timestamps may be lost. This patch writes the recent timestamp into the page that is passed back to the caller. A partial ring_buffer_page_read is where the full page would not be written back to the user, and instead, just part of the page is copied to the user. A full page would be a page swap with the ring buffer and the timestamps would be correct. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 12:52:42 +08:00
bpage->time_stamp = save_timestamp;
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
ring-buffer: make ring_buffer_read_page read from start on partial page Impact: dont leave holes in read buffer page The ring_buffer_read_page swaps a given page with the reader page of the ring buffer, if certain conditions are set: 1) requested length is big enough to hold entire page data 2) a writer is not currently on the page 3) the page is not partially consumed. Instead of swapping with the supplied page. It copies the data to the supplied page instead. But currently the data is copied in the same offset as the source page. This causes a hole at the start of the reader page. This complicates the use of this function. Instead, it should copy the data at the beginning of the function and update the index fields accordingly. Other small clean ups are also done in this patch. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-04 08:51:40 +08:00
/* we copied everything to the beginning */
read = 0;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
} else {
ring-buffer: have read page swap increment counter with page entries In the swap page ring buffer code that is used by the ftrace splice code, we scan the page to increment the counter of entries read. With the number of entries already in the page we simply need to add it. [ Impact: speed up reading page from ring buffer ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-02 07:40:05 +08:00
/* update the entry counter */
ring-buffer: make lockless This patch converts the ring buffers into a completely lockless buffer recording system. The read side still takes locks since we still serialize readers. But the writers are the ones that must be lockless (those can happen in NMIs). The main change is to the "head_page" pointer. We write to the tail, and read from the head. The "head_page" pointer in the cpu buffer is now just a reference to where to look. The real head page is now kept in the head_page->list->prev->next pointer. That is, in the list head of the previous page we set flags. The list pages are allocated to be aligned such that the lowest significant bits are always zero pointing to the list. This gives us play to put in flags to their pointers. bit 0: set when the page is a head page bit 1: set when the writer is moving the page (for overwrite mode) cmpxchg is used to update the pointer. When the writer wraps the buffer and the tail meets the head, in overwrite mode, the writer must move the head page forward. It first uses cmpxchg to change the pointer flag from 1 to 2. Once this is done, the reader on another CPU will not take the page from the buffer. The writers need to protect against interrupts (we don't bother with disabling interrupts because NMIs are allowed to write too). After the writer sets the pointer flag to 2, it takes care to manage interrupts coming in. This is discribed in detail within the comments of the code. Changes in version 2: - Let reader reset entries value of header page. - Fix tail page passing commit page on reader page test. - Always increment entries and write counter in rb_tail_page_update - Add safety check in rb_set_commit_to_write to break out of infinite loop - add mask in rb_is_reader_page [ Impact: lock free writing to the ring buffer ] Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-27 23:00:29 +08:00
cpu_buffer->read += rb_page_entries(reader);
ring-buffer: have read page swap increment counter with page entries In the swap page ring buffer code that is used by the ftrace splice code, we scan the page to increment the counter of entries read. With the number of entries already in the page we simply need to add it. [ Impact: speed up reading page from ring buffer ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-02 07:40:05 +08:00
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
/* swap the pages */
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
rb_init_page(bpage);
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
bpage = reader->page;
reader->page = *data_page;
local_set(&reader->write, 0);
ring-buffer: record page entries in buffer page descriptor Currently, when the ring buffer writer overflows the buffer and must write over non consumed data, we increment the overrun counter by reading the entries on the page we are about to overwrite. This reads the entries one by one. This is not very effecient. This patch adds another entry counter into each buffer page descriptor that keeps track of the number of entries on the page. Now on overwrite, the overrun counter simply needs to add the number of entries that is on the page it is about to overwrite. [ Impact: speed up of ring buffer in overwrite mode ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-02 06:44:45 +08:00
local_set(&reader->entries, 0);
ring-buffer: fix ring_buffer_read_page The ring_buffer_read_page was broken if it were to only copy part of the page. This patch fixes that up as well as adds a parameter to allow a length field, in order to only copy part of the buffer page. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-03 13:27:49 +08:00
reader->read = 0;
ring-buffer: change "page" variable names to "bpage" Impact: clean up Andrew Morton pointed out that the kernel convention of a variable named page should be of type page struct. The ring buffer uses a variable named "page" for a pointer to something else. This patch converts those to be called "bpage" (as in "buffer page"). Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 12:50:03 +08:00
*data_page = bpage;
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
/*
* Use the real_end for the data size,
* This gives us a chance to store the lost events
* on the page.
*/
if (reader->real_end)
local_set(&bpage->commit, reader->real_end);
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
}
ring_buffer: fix ring_buffer_read_page() Impact: change API and init bpage when copy ring_buffer_read_page()/rb_remove_entries() may be called for a partially consumed page. Add a parameter for rb_remove_entries() and make it update cpu_buffer->entries correctly for partially consumed pages. ring_buffer_read_page() now returns the offset to the next event. Init the bpage's time_stamp when return value is 0. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-02-09 14:21:17 +08:00
ret = read;
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
cpu_buffer->lost_events = 0;
ring-buffer: Move zeroing out excess in page to ring buffer code Currently the trace splice code zeros out the excess bytes in the page before sending it off to userspace. This is to make sure userspace is not getting anything it should not be when reading the pages, because the excess data was never initialized to zero before writing (for perfomance reasons). But the splice code has no business in doing this work, it should be done by the ring buffer. With the latest changes for recording lost events, the splice code gets it wrong anyway. Move the zeroing out of excess bytes into the ring buffer code. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-05-22 01:32:26 +08:00
commit = local_read(&bpage->commit);
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
/*
* Set a flag in the commit field if we lost events
*/
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
if (missed_events) {
/* If there is room at the end of the page to save the
* missed events, then record it there.
*/
if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
memcpy(&bpage->data[commit], &missed_events,
sizeof(missed_events));
local_add(RB_MISSED_STORED, &bpage->commit);
ring-buffer: Move zeroing out excess in page to ring buffer code Currently the trace splice code zeros out the excess bytes in the page before sending it off to userspace. This is to make sure userspace is not getting anything it should not be when reading the pages, because the excess data was never initialized to zero before writing (for perfomance reasons). But the splice code has no business in doing this work, it should be done by the ring buffer. With the latest changes for recording lost events, the splice code gets it wrong anyway. Move the zeroing out of excess bytes into the ring buffer code. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-05-22 01:32:26 +08:00
commit += sizeof(missed_events);
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
}
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
local_add(RB_MISSED_EVENTS, &bpage->commit);
ring-buffer: Add lost event count to end of sub buffer Currently, binary readers of the ring buffer only know where events were lost, but not how many events were lost at that location. This information is available, but it would require adding another field to the sub buffer header to include it. But when a event can not fit at the end of a sub buffer, it is written to the next sub buffer. This means there is a good chance that the buffer may have room to hold this counter. If it does, write the counter at the end of the sub buffer and set another flag in the data size field that states that this information exists. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 10:11:42 +08:00
}
ring-buffer: Add place holder recording of dropped events Currently, when the ring buffer drops events, it does not record the fact that it did so. It does inform the writer that the event was dropped by returning a NULL event, but it does not put in any place holder where the event was dropped. This is not a trivial thing to add because the ring buffer mostly runs in overwrite (flight recorder) mode. That is, when the ring buffer is full, new data will overwrite old data. In a produce/consumer mode, where new data is simply dropped when the ring buffer is full, it is trivial to add the placeholder for dropped events. When there's more room to write new data, then a special event can be added to notify the reader about the dropped events. But in overwrite mode, any new write can overwrite events. A place holder can not be inserted into the ring buffer since there never may be room. A reader could also come in at anytime and miss the placeholder. Luckily, the way the ring buffer works, the read side can find out if events were lost or not, and how many events. Everytime a write takes place, if it overwrites the header page (the next read) it updates a "overrun" variable that keeps track of the number of lost events. When a reader swaps out a page from the ring buffer, it can record this number, perfom the swap, and then check to see if the number changed, and take the diff if it has, which would be the number of events dropped. This can be stored by the reader and returned to callers of the reader. Since the reader page swap will fail if the writer moved the head page since the time the reader page set up the swap, this gives room to record the overruns without worrying about races. If the reader sets up the pages, records the overrun, than performs the swap, if the swap succeeds, then the overrun variable has not been updated since the setup before the swap. For binary readers of the ring buffer, a flag is set in the header of each sub page (sub buffer) of the ring buffer. This flag is embedded in the size field of the data on the sub buffer, in the 31st bit (the size can be 32 or 64 bits depending on the architecture), but only 27 bits needs to be used for the actual size (less actually). We could add a new field in the sub buffer header to also record the number of events dropped since the last read, but this will change the format of the binary ring buffer a bit too much. Perhaps this change can be made if the information on the number of events dropped is considered important enough. Note, the notification of dropped events is only used by consuming reads or peeking at the ring buffer. Iterating over the ring buffer does not keep this information because the necessary data is only available when a page swap is made, and the iterator does not swap out pages. Cc: Robert Richter <robert.richter@amd.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-04-01 01:21:56 +08:00
ring-buffer: Move zeroing out excess in page to ring buffer code Currently the trace splice code zeros out the excess bytes in the page before sending it off to userspace. This is to make sure userspace is not getting anything it should not be when reading the pages, because the excess data was never initialized to zero before writing (for perfomance reasons). But the splice code has no business in doing this work, it should be done by the ring buffer. With the latest changes for recording lost events, the splice code gets it wrong anyway. Move the zeroing out of excess bytes into the ring buffer code. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-05-22 01:32:26 +08:00
/*
* This page may be off to user land. Zero it out here.
*/
if (commit < BUF_PAGE_SIZE)
memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
out_unlock:
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
out:
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
return ret;
}
ring-buffer: export symbols I'm adding a module to do a series of tests on the ring buffer as well as benchmarks. This module needs to have more of the ring buffer API exported. There's nothing wrong with reading the ring buffer from a module. [ Impact: allow modules to read pages from the ring buffer ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-05-05 13:15:24 +08:00
EXPORT_SYMBOL_GPL(ring_buffer_read_page);
ring-buffer: read page interface Impact: new API to ring buffer This patch adds a new interface into the ring buffer that allows a page to be read from the ring buffer on a given CPU. For every page read, one must also be given to allow for a "swap" of the pages. rpage = ring_buffer_alloc_read_page(buffer); if (!rpage) goto err; ret = ring_buffer_read_page(buffer, &rpage, cpu, full); if (!ret) goto empty; process_page(rpage); ring_buffer_free_read_page(rpage); The caller of these functions must handle any waits that are needed to wait for new data. The ring_buffer_read_page will simply return 0 if there is no data, or if "full" is set and the writer is still on the current page. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 04:34:07 +08:00
ring-buffer: Make it generally available In hunting down the cause for the hwlat_detector ring buffer spew in my failed -next builds it became obvious that folks are now treating ring_buffer as something that is generic independent of tracing and thus, suitable for public driver consumption. Given that there are only a few minor areas in ring_buffer that have any reliance on CONFIG_TRACING or CONFIG_FUNCTION_TRACER, provide stubs for those and make it generally available. Signed-off-by: Paul Mundt <lethal@linux-sh.org> Cc: Jon Masters <jcm@jonmasters.org> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <20090625053012.GB19944@linux-sh.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-06-25 13:30:12 +08:00
#ifdef CONFIG_TRACING
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
static ssize_t
rb_simple_read(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
tracing: fix sparse warnings: fix (un-)signedness Fix these sparse warnings: kernel/trace/ring_buffer.c:70:37: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:84:39: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:96:43: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2475:13: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2475:13: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2478:42: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2478:42: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2500:40: warning: incorrect type in argument 3 (different signedness) kernel/trace/ring_buffer.c:2505:44: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2507:46: warning: incorrect type in argument 2 (different signedness) kernel/trace/trace.c:2130:40: warning: incorrect type in argument 3 (different signedness) kernel/trace/trace.c:2280:40: warning: incorrect type in argument 3 (different signedness) Signed-off-by: Hannes Eder <hannes@hanneseder.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-11 02:44:34 +08:00
unsigned long *p = filp->private_data;
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
char buf[64];
int r;
ring-buffer: add tracing_off_permanent Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-22 01:41:55 +08:00
if (test_bit(RB_BUFFERS_DISABLED_BIT, p))
r = sprintf(buf, "permanently disabled\n");
else
r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p));
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}
static ssize_t
rb_simple_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
tracing: fix sparse warnings: fix (un-)signedness Fix these sparse warnings: kernel/trace/ring_buffer.c:70:37: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:84:39: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:96:43: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2475:13: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2475:13: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2478:42: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2478:42: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2500:40: warning: incorrect type in argument 3 (different signedness) kernel/trace/ring_buffer.c:2505:44: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2507:46: warning: incorrect type in argument 2 (different signedness) kernel/trace/trace.c:2130:40: warning: incorrect type in argument 3 (different signedness) kernel/trace/trace.c:2280:40: warning: incorrect type in argument 3 (different signedness) Signed-off-by: Hannes Eder <hannes@hanneseder.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-11 02:44:34 +08:00
unsigned long *p = filp->private_data;
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
char buf[64];
tracing: fix sparse warnings: fix (un-)signedness Fix these sparse warnings: kernel/trace/ring_buffer.c:70:37: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:84:39: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:96:43: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2475:13: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2475:13: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2478:42: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2478:42: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2500:40: warning: incorrect type in argument 3 (different signedness) kernel/trace/ring_buffer.c:2505:44: warning: incorrect type in argument 2 (different signedness) kernel/trace/ring_buffer.c:2507:46: warning: incorrect type in argument 2 (different signedness) kernel/trace/trace.c:2130:40: warning: incorrect type in argument 3 (different signedness) kernel/trace/trace.c:2280:40: warning: incorrect type in argument 3 (different signedness) Signed-off-by: Hannes Eder <hannes@hanneseder.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-11 02:44:34 +08:00
unsigned long val;
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
int ret;
if (cnt >= sizeof(buf))
return -EINVAL;
if (copy_from_user(&buf, ubuf, cnt))
return -EFAULT;
buf[cnt] = 0;
ret = strict_strtoul(buf, 10, &val);
if (ret < 0)
return ret;
ring-buffer: add tracing_off_permanent Impact: feature to permanently disable ring buffer This patch adds a API to the ring buffer code that will permanently disable the ring buffer from ever recording. This should only be called when some serious anomaly is detected, and the system may be in an unstable state. When that happens, shutting down the recording to the ring buffers may be appropriate. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-22 01:41:55 +08:00
if (val)
set_bit(RB_BUFFERS_ON_BIT, p);
else
clear_bit(RB_BUFFERS_ON_BIT, p);
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
(*ppos)++;
return cnt;
}
tracing: make all file_operations const Impact: cleanup All file_operations structures should be constant. No one is going to change them. Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-06 10:44:55 +08:00
static const struct file_operations rb_simple_fops = {
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
.open = tracing_open_generic,
.read = rb_simple_read,
.write = rb_simple_write,
};
static __init int rb_init_debugfs(void)
{
struct dentry *d_tracer;
d_tracer = tracing_init_dentry();
tracing/ftrace: factorize the tracing files creation Impact: cleanup Most of the tracing files creation follow the same pattern: ret = debugfs_create_file(...) if (!ret) pr_warning("Couldn't create ... entry\n") Unify it! Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <1238109938-11840-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-03-27 07:25:38 +08:00
trace_create_file("tracing_on", 0644, d_tracer,
&ring_buffer_flags, &rb_simple_fops);
ring-buffer: buffer record on/off switch Impact: enable/disable ring buffer recording API added Several kernel developers have requested that there be a way to stop recording into the ring buffers with a simple switch that can also be enabled from userspace. This patch addes a new kernel API to the ring buffers called: tracing_on() tracing_off() When tracing_off() is called, all ring buffers will not be able to record into their buffers. tracing_on() will enable the ring buffers again. These two act like an on/off switch. That is, there is no counting of the number of times tracing_off or tracing_on has been called. A new file is added to the debugfs/tracing directory called tracing_on This allows for userspace applications to also flip the switch. echo 0 > debugfs/tracing/tracing_on disables the tracing. echo 1 > /debugfs/tracing/tracing_on enables it. Note, this does not disable or enable any tracers. It only sets or clears a flag that needs to be set in order for the ring buffers to write to their buffers. It is a global flag, and affects all ring buffers. The buffers start out with tracing_on enabled. There are now three flags that control recording into the buffers: tracing_on: which affects all ring buffer tracers. buffer->record_disabled: which affects an allocated buffer, which may be set if an anomaly is detected, and tracing is disabled. cpu_buffer->record_disabled: which is set by tracing_stop() or if an anomaly is detected. tracing_start can not reenable this if an anomaly occurred. The userspace debugfs/tracing/tracing_enabled is implemented with tracing_stop() but the user space code can not enable it if the kernel called tracing_stop(). Userspace can enable the tracing_on even if the kernel disabled it. It is just a switch used to stop tracing if a condition was hit. tracing_on is not for protecting critical areas in the kernel nor is it for stopping tracing if an anomaly occurred. This is because userspace can reenable it at any time. Side effect: With this patch, I discovered a dead variable in ftrace.c called tracing_on. This patch removes it. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2008-11-12 04:01:42 +08:00
return 0;
}
fs_initcall(rb_init_debugfs);
ring-buffer: Make it generally available In hunting down the cause for the hwlat_detector ring buffer spew in my failed -next builds it became obvious that folks are now treating ring_buffer as something that is generic independent of tracing and thus, suitable for public driver consumption. Given that there are only a few minor areas in ring_buffer that have any reliance on CONFIG_TRACING or CONFIG_FUNCTION_TRACER, provide stubs for those and make it generally available. Signed-off-by: Paul Mundt <lethal@linux-sh.org> Cc: Jon Masters <jcm@jonmasters.org> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <20090625053012.GB19944@linux-sh.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-06-25 13:30:12 +08:00
#endif
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
ring-buffer: use CONFIG_HOTPLUG_CPU not CONFIG_HOTPLUG The hotplug code in the ring buffers is for use with CPU hotplug, not generic hotplug. Reported-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 23:46:03 +08:00
#ifdef CONFIG_HOTPLUG_CPU
tracing/ring-buffer: don't annotate rb_cpu_notify with __cpuinit Impact: remove a section warning CONFIG_DEBUG_SECTION_MISMATCH raises the following warning on -tip: WARNING: kernel/trace/built-in.o(.text+0x5bc5): Section mismatch in reference from the function ring_buffer_alloc() to the function .cpuinit.text:rb_cpu_notify() The function ring_buffer_alloc() references the function __cpuinit rb_cpu_notify(). This is actually harmless. The code in the ring buffer don't build rb_cpu_notify and other cpu hotplug stuffs when !CONFIG_HOTPLUG_CPU so we have no risk to reference freed memory here (it would even be harmless if we unconditionally build it because register_cpu_notifier would do nothing when !CONFIG_HOTPLUG_CPU. But since ring_buffer_alloc() can be called everytime, we don't want it to be annotated with __cpuinit so we drop the __cpuinit from rb_cpu_notify. This is not a waste of memory because it is only defined and used on CONFIG_HOTPLUG_CPU. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <1237606416-22268-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-03-21 11:33:36 +08:00
static int rb_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
{
struct ring_buffer *buffer =
container_of(self, struct ring_buffer, cpu_notify);
long cpu = (long)hcpu;
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
cpumask: use new operators in kernel/trace Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> LKML-Reference: <200906122115.30787.rusty@rustcorp.com.au> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-12 19:45:30 +08:00
if (cpumask_test_cpu(cpu, buffer->cpumask))
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
return NOTIFY_OK;
buffer->buffers[cpu] =
rb_allocate_cpu_buffer(buffer, cpu);
if (!buffer->buffers[cpu]) {
WARN(1, "failed to allocate ring buffer on CPU %ld\n",
cpu);
return NOTIFY_OK;
}
smp_wmb();
cpumask: use new operators in kernel/trace Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> LKML-Reference: <200906122115.30787.rusty@rustcorp.com.au> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-12 19:45:30 +08:00
cpumask_set_cpu(cpu, buffer->cpumask);
ring-buffer: only allocate buffers for online cpus Impact: save on memory Currently, a ring buffer was allocated for each "possible_cpus". On some systems, this is the same as NR_CPUS. Thus, if a system defined NR_CPUS = 64 but it only had 1 CPU, we could have possibly 63 useless ring buffers taking up space. With a default buffer of 3 megs, this could be quite drastic. This patch changes the ring buffer code to only allocate ring buffers for online CPUs. If a CPU goes off line, we do not free the buffer. This is because the user may still have trace data in that buffer that they would like to look at. Perhaps in the future we could add code to delete a ring buffer if the CPU is offline and the ring buffer becomes empty. Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-03-12 10:00:13 +08:00
break;
case CPU_DOWN_PREPARE:
case CPU_DOWN_PREPARE_FROZEN:
/*
* Do nothing.
* If we were to free the buffer, then the user would
* lose any trace that was in the buffer.
*/
break;
default:
break;
}
return NOTIFY_OK;
}
#endif