When I mounted an NFS directory, it caused several modules to be loaded. At the
time I was running the preemptirqsoff tracer, and it showed the following
output:
# tracer: preemptirqsoff
#
# preemptirqsoff latency trace v1.1.5 on 2.6.33.9-rt30-mrg-test
# --------------------------------------------------------------------
# latency: 1177 us, #4/4, CPU#3 | (M:preempt VP:0, KP:0, SP:0 HP:0 #P:4)
# -----------------
# | task: modprobe-19370 (uid:0 nice:0 policy:0 rt_prio:0)
# -----------------
# => started at: ftrace_module_notify
# => ended at: ftrace_module_notify
#
#
# _------=> CPU#
# / _-----=> irqs-off
# | / _----=> need-resched
# || / _---=> hardirq/softirq
# ||| / _--=> preempt-depth
# |||| /_--=> lock-depth
# |||||/ delay
# cmd pid |||||| time | caller
# \ / |||||| \ | /
modprobe-19370 3d.... 0us!: ftrace_process_locs <-ftrace_module_notify
modprobe-19370 3d.... 1176us : ftrace_process_locs <-ftrace_module_notify
modprobe-19370 3d.... 1178us : trace_hardirqs_on <-ftrace_module_notify
modprobe-19370 3d.... 1178us : <stack trace>
=> ftrace_process_locs
=> ftrace_module_notify
=> notifier_call_chain
=> __blocking_notifier_call_chain
=> blocking_notifier_call_chain
=> sys_init_module
=> system_call_fastpath
That's over 1ms that interrupts are disabled on a Real-Time kernel!
Looking at the cause (being the ftrace author helped), I found that the
interrupts are disabled before the code modification of mcounts into nops. The
interrupts only need to be disabled on start up around this code, not when
modules are being loaded.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
If a function is set to be traced by the set_graph_function, but the
option funcgraph-irqs is zero, and the traced function happens to be
called from a interrupt, it will not be traced.
The point of funcgraph-irqs is to not trace interrupts when we are
preempted by an irq, not to not trace functions we want to trace that
happen to be *in* a irq.
Luckily the current->trace_recursion element is perfect to add a flag
to help us be able to trace functions within an interrupt even when
we are not tracing interrupts that preempt the trace.
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
KVM needs one-shot samples, since a PMC programmed to -X will fire after X
events and then again after 2^40 events (i.e. variable period).
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1309362157-6596-4-git-send-email-avi@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The perf_event overflow handler does not receive any caller-derived
argument, so many callers need to resort to looking up the perf_event
in their local data structure. This is ugly and doesn't scale if a
single callback services many perf_events.
Fix by adding a context parameter to perf_event_create_kernel_counter()
(and derived hardware breakpoints APIs) and storing it in the perf_event.
The field can be accessed from the callback as event->overflow_handler_context.
All callers are updated.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1309362157-6596-2-git-send-email-avi@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Since only samples call perf_output_sample() its much saner (and more
correct) to put the sample logic in there than in the
perf_output_begin()/perf_output_end() pair.
Saves a useless argument, reduces conditionals and shrinks
struct perf_output_handle, win!
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-2crpvsx3cqu67q3zqjbnlpsc@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The nmi parameter indicated if we could do wakeups from the current
context, if not, we would set some state and self-IPI and let the
resulting interrupt do the wakeup.
For the various event classes:
- hardware: nmi=0; PMI is in fact an NMI or we run irq_work_run from
the PMI-tail (ARM etc.)
- tracepoint: nmi=0; since tracepoint could be from NMI context.
- software: nmi=[0,1]; some, like the schedule thing cannot
perform wakeups, and hence need 0.
As one can see, there is very little nmi=1 usage, and the down-side of
not using it is that on some platforms some software events can have a
jiffy delay in wakeup (when arch_irq_work_raise isn't implemented).
The up-side however is that we can remove the nmi parameter and save a
bunch of conditionals in fast paths.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Michael Cree <mcree@orcon.net.nz>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Don Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/n/tip-agjev8eu666tvknpb3iaj0fg@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Due to restriction and specifics of Netburst PMU we need a separated
event for NMI watchdog. In particular every Netburst event
consumes not just a counter and a config register, but also an
additional ESCR register.
Since ESCR registers are grouped upon counters (i.e. if ESCR is occupied
for some event there is no room for another event to enter until its
released) we need to pick up the "least" used ESCR (or the most available
one) for nmi-watchdog purposes -- so MSR_P4_CRU_ESCR2/3 was chosen.
With this patch nmi-watchdog and perf top should be able to run simultaneously.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Lin Ming <ming.m.lin@intel.com>
CC: Arnaldo Carvalho de Melo <acme@redhat.com>
CC: Frederic Weisbecker <fweisbec@gmail.com>
Tested-and-reviewed-by: Don Zickus <dzickus@redhat.com>
Tested-and-reviewed-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110623124918.GC13050@sun
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The event tracing infrastructure exposes two timers which should be updated
each time the value of the counter is updated. Currently, these counters are
only updated when userspace calls read() on the fd associated with an event.
This means that counters which are read via the mmap'd page exclusively never
have their timers updated. This patch adds ensures that the timers are updated
each time the values in the mmap'd page are updated.
Signed-off-by: Eric B Munson <emunson@mgebm.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1308932786-5111-1-git-send-email-emunson@mgebm.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Take the timer calculation from perf_output_read and move it to a helper
function for any place that needs timer values but cannot take the ctx->lock.
Signed-off-by: Eric B Munson <emunson@mgebm.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1308861279-15216-2-git-send-email-emunson@mgebm.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Since 2.6.36 (specifically commit d57e34fdd6 ("perf: Simplify the
ring-buffer logic: make perf_buffer_alloc() do everything needed"),
the perf_buffer_init_code() has been mis-setting the buffer watermark
if perf_event_attr.wakeup_events has a non-zero value.
This is because perf_event_attr.wakeup_events is a union with
perf_event_attr.wakeup_watermark.
This commit re-enables the check for perf_event_attr.watermark being
set before continuing with setting a non-default watermark.
This bug is most noticable when you are trying to use PERF_IOC_REFRESH
with a value larger than one and perf_event_attr.wakeup_events is set to
one. In this case the buffer watermark will be set to 1 and you will
get extraneous POLL_IN overflows rather than POLL_HUP as expected.
[ avoid using attr.wakeup_events when attr.watermark is set ]
Signed-off-by: Vince Weaver <vweaver1@eecs.utk.edu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.00.1106011506390.5384@cl320.eecs.utk.edu
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Currently a single process may register exit handlers unlimited times.
It may lead to a bloated listeners chain and very slow process
terminations.
Eg after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of
kernel memory is stolen for the handlers chain and "time id" shows 2-7
seconds instead of normal 0.003. It makes it possible to exhaust all
kernel memory and to eat much of CPU time by triggerring numerous exits
on a single CPU.
The patch limits the number of times a single process may register
itself on a single CPU to one.
One little issue is kept unfixed - as taskstats_exit() is called before
exit_files() in do_exit(), the orphaned listener entry (if it was not
explicitly deregistered) is kept until the next someone's exit() and
implicit deregistration in send_cpu_listeners(). So, if a process
registered itself as a listener exits and the next spawned process gets
the same pid, it would inherit taskstats attributes.
Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Toralf Förster and Richard Weinberger noted that if there is
no RTC device, the alarm timers core prints out an annoying
"ALARM timers will not wake from suspend" message.
This warning has been removed in a previous patch, however
the issue still remains: The original idea was to support
alarm timers even if there was no rtc device, as long as the
system didn't go into suspend.
However, after further consideration, communicating to the application
that alarmtimers are not fully functional seems like the better
solution.
So this patch makes it so we return -ENOTSUPP to any posix _ALARM
clockid calls if there is no backing RTC device on the system.
Further this changes the behavior where when there is no rtc device
we will check for one on clock_getres, clock_gettime, timer_create,
and timer_nsleep instead of on suspend.
CC: Toralf Förster <toralf.foerster@gmx.de>
CC: Richard Weinberger <richard@nod.at
CC: Peter Zijlstra <peterz@infradead.org>
CC: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Reported by: Richard Weinberger <richard@nod.at>
Signed-off-by: John Stultz <john.stultz@linaro.org>
The alarmtimers code currently picks a rtc device to use at
late init time. However, if your rtc driver is loaded as a module,
it may be registered after the alarmtimers late init code, leaving
the alarmtimers nonfunctional.
This patch moves the the rtcdevice selection to when we actually try
to use it, allowing us to make use of rtc modules that may have been
loaded at any point since bootup.
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Meelis Roos <mroos@ut.ee>
Reported-by: Meelis Roos <mroos@ut.ee>
Signed-off-by: John Stultz <john.stultz@linaro.org>
When opening /dev/snapshot device, snapshot_open() creates memory
bitmaps which are freed in snapshot_release(). But if any of the
callbacks called by pm_notifier_call_chain() returns NOTIFY_BAD, open()
fails, snapshot_release() is never called and bitmaps are not freed.
Next attempt to open /dev/snapshot then triggers BUG_ON() check in
create_basic_memory_bitmaps(). This happens e.g. when vmwatchdog module
is active on s390x.
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: stable@kernel.org
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
tools/perf: Fix static build of perf tool
tracing: Fix regression in printk_formats file
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
generic-ipi: Fix kexec boot crash by initializing call_single_queue before enabling interrupts
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
clocksource: Make watchdog robust vs. interruption
timerfd: Fix wakeup of processes when timer is cancelled on clock change
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
x86, MAINTAINERS: Add x86 MCE people
x86, efi: Do not reserve boot services regions within reserved areas
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
rcu: Move RCU_BOOST #ifdefs to header file
rcu: use softirq instead of kthreads except when RCU_BOOST=y
rcu: Use softirq to address performance regression
rcu: Simplify curing of load woes
____call_usermodehelper() now erases any credentials set by the
subprocess_inf::init() function. The problem is that commit
17f60a7da1 ("capabilites: allow the application of capability limits
to usermode helpers") creates and commits new credentials with
prepare_kernel_cred() after the call to the init() function. This wipes
all keyrings after umh_keys_init() is called.
The best way to deal with this is to put the init() call just prior to
the commit_creds() call, and pass the cred pointer to init(). That
means that umh_keys_init() and suchlike can modify the credentials
_before_ they are published and potentially in use by the rest of the
system.
This prevents request_key() from working as it is prevented from passing
the session keyring it set up with the authorisation token to
/sbin/request-key, and so the latter can't assume the authority to
instantiate the key. This causes the in-kernel DNS resolver to fail
with ENOKEY unconditionally.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Tested-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is a problem that kdump(2nd kernel) sometimes hangs up due
to a pending IPI from 1st kernel. Kernel panic occurs because IPI
comes before call_single_queue is initialized.
To fix the crash, rename init_call_single_data() to call_function_init()
and call it in start_kernel() so that call_single_queue can be
initialized before enabling interrupts.
The details of the crash are:
(1) 2nd kernel boots up
(2) A pending IPI from 1st kernel comes when irqs are first enabled
in start_kernel().
(3) Kernel tries to handle the interrupt, but call_single_queue
is not initialized yet at this point. As a result, in the
generic_smp_call_function_single_interrupt(), NULL pointer
dereference occurs when list_replace_init() tries to access
&q->list.next.
Therefore this patch changes the name of init_call_single_data()
to call_function_init() and calls it before local_irq_enable()
in start_kernel().
Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Milton Miller <miltonm@bga.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: kexec@lists.infradead.org
Link: http://lkml.kernel.org/r/D6CBEE2F420741indou.takao@jp.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The commit "use softirq instead of kthreads except when RCU_BOOST=y"
just applied #ifdef in place. This commit is a cleanup that moves
the newly #ifdef'ed code to the header file kernel/rcutree_plugin.h.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The clocksource watchdog code is interruptible and it has been
observed that this can trigger false positives which disable the TSC.
The reason is that an interrupt storm or a long running interrupt
handler between the read of the watchdog source and the read of the
TSC brings the two far enough apart that the delta is larger than the
unstable treshold. Move both reads into a short interrupt disabled
region to avoid that.
Reported-and-tested-by: Vernon Mauery <vernux@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org
This patch #ifdefs RCU kthreads out of the kernel unless RCU_BOOST=y,
thus eliminating context-switch overhead if RCU priority boosting has
not been configured.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
sched: Check if lowest_mask is initialized in find_lowest_rq()
sched: Fix need_resched() when checking peempt
CONFIG_CONSTRUCTORS controls support for running constructor functions at
kernel init time. According to commit b99b87f70c ("kernel:
constructor support"), gcov (CONFIG_GCOV_KERNEL) needs this. However,
CONFIG_CONSTRUCTORS currently defaults to y, with no option to disable it,
and CONFIG_GCOV_KERNEL depends on it. Instead, default it to n and have
CONFIG_GCOV_KERNEL select it, so that the normal case of
CONFIG_GCOV_KERNEL=n will result in CONFIG_CONSTRUCTORS=n.
Observed in the short list of =y values in a minimal kernel configuration.
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The following crash was reported:
> Call Trace:
> [<ffffffff81139792>] mem_cgroup_from_task+0x15/0x17
> [<ffffffff8113a75a>] __mem_cgroup_try_charge+0x148/0x4b4
> [<ffffffff810493f3>] ? need_resched+0x23/0x2d
> [<ffffffff814cbf43>] ? preempt_schedule+0x46/0x4f
> [<ffffffff8113afe8>] mem_cgroup_charge_common+0x9a/0xce
> [<ffffffff8113b6d1>] mem_cgroup_newpage_charge+0x5d/0x5f
> [<ffffffff81134024>] khugepaged+0x5da/0xfaf
> [<ffffffff81078ea0>] ? __init_waitqueue_head+0x4b/0x4b
> [<ffffffff81133a4a>] ? add_mm_counter.constprop.5+0x13/0x13
> [<ffffffff81078625>] kthread+0xa8/0xb0
> [<ffffffff814d13e8>] ? sub_preempt_count+0xa1/0xb4
> [<ffffffff814d5664>] kernel_thread_helper+0x4/0x10
> [<ffffffff814ce858>] ? retint_restore_args+0x13/0x13
> [<ffffffff8107857d>] ? __init_kthread_worker+0x5a/0x5a
What happens is that khugepaged tries to charge a huge page against an mm
whose last possible owner has already exited, and the memory controller
crashes when the stale mm->owner is used to look up the cgroup to charge.
mm->owner has never been set to NULL with the last owner going away, but
nobody cared until khugepaged came along.
Even then it wasn't a problem because the final mmput() on an mm was
forced to acquire and release mmap_sem in write-mode, preventing an
exiting owner to go away while the mmap_sem was held, and until "692e0b3
mm: thp: optimize memcg charge in khugepaged", the memory cgroup charge
was protected by mmap_sem in read-mode.
Instead of going back to relying on the mmap_sem to enforce lifetime of a
task, this patch ensures that mm->owner is properly set to NULL when the
last possible owner is exiting, which the memory controller can handle
just fine.
[akpm@linux-foundation.org: tweak comments]
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Hugh Dickins <hughd@google.com>
Reported-by: Dave Jones <davej@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On system boot up, the lowest_mask is initialized with an
early_initcall(). But RT tasks may wake up on other
early_initcall() callers before the lowest_mask is initialized,
causing a system crash.
Commit "d72bce0e67 rcu: Cure load woes" was the first commit
to wake up RT tasks in early init. Before this commit this bug
should not happen.
Reported-by: Andrew Theurer <habanero@linux.vnet.ibm.com>
Tested-by: Andrew Theurer <habanero@linux.vnet.ibm.com>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20110614223657.824872966@goodmis.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The RT preempt check tests the wrong task if NEED_RESCHED is
set. It currently checks the local CPU task. It is supposed to
check the task that is running on the runqueue we are about to
wake another task on.
Signed-off-by: Hillf Danton <dhillf@gmail.com>
Reviewed-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20110614223657.450239027@goodmis.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Fix to support kernel stack trace correctly on kprobe-tracer.
Since the execution path of kprobe-based dynamic events is different
from other tracepoint-based events, normal ftrace_trace_stack() doesn't
work correctly. To fix that, this introduces ftrace_trace_stack_regs()
which traces stack via pt_regs instead of current stack register.
e.g.
# echo p schedule+4 > /sys/kernel/debug/tracing/kprobe_events
# echo 1 > /sys/kernel/debug/tracing/options/stacktrace
# echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable
# head -n 20 /sys/kernel/debug/tracing/trace
bash-2968 [000] 10297.050245: p_schedule_4: (schedule+0x4/0x4ca)
bash-2968 [000] 10297.050247: <stack trace>
=> schedule_timeout
=> n_tty_read
=> tty_read
=> vfs_read
=> sys_read
=> system_call_fastpath
kworker/0:1-2940 [000] 10297.050265: p_schedule_4: (schedule+0x4/0x4ca)
kworker/0:1-2940 [000] 10297.050266: <stack trace>
=> worker_thread
=> kthread
=> kernel_thread_helper
sshd-1132 [000] 10297.050365: p_schedule_4: (schedule+0x4/0x4ca)
sshd-1132 [000] 10297.050365: <stack trace>
=> sysret_careful
Note: Even with this fix, the first entry will be skipped
if the probe is put on the function entry area before
the frame pointer is set up (usually, that is 4 bytes
(push %bp; mov %sp %bp) on x86), because stack unwinder
depends on the frame pointer.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@gmail.com>
Link: http://lkml.kernel.org/r/20110608070934.17777.17116.stgit@fedora15
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Add weak symbol of save_stack_trace_regs() as same as
save_stack_trace_tsk() since that is not implemented
except x86 yet.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@gmail.com>
Link: http://lkml.kernel.org/r/20110608070927.17777.37895.stgit@fedora15
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The tracing ring buffer is allocated from kernel memory. While
allocating a large chunk of memory, OOM might happen which destabilizes
the system. Thus random processes might get killed during the
allocation.
This patch adds __GFP_NORETRY flag to the ring buffer allocation calls
to make it fail more gracefully if the system will not be able to
complete the allocation request.
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Link: http://lkml.kernel.org/r/1307491302-9236-1-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This patch replaces the code for getting an unsigned long from a
userspace buffer by a simple call to kstroul_from_user.
This makes it easier to read and less error prone.
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Link: http://lkml.kernel.org/r/1307476707-14762-1-git-send-email-peterhuewe@gmx.de
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The function_graph tracer does not follow global context-info option.
Adding TRACE_ITER_CONTEXT_INFO trace_flags check to enable it.
With following commands:
# echo function_graph > ./current_tracer
# echo 0 > options/context-info
# cat trace
This is what it looked like before:
# tracer: function_graph
#
# TIME CPU DURATION FUNCTION CALLS
# | | | | | | | |
1) 0.079 us | } /* __vma_link_rb */
1) 0.056 us | copy_page_range();
1) | security_vm_enough_memory() {
...
This is what it looks like now:
# tracer: function_graph
#
} /* update_ts_time_stats */
timekeeping_max_deferment();
...
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1307113131-10045-6-git-send-email-jolsa@redhat.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The header display of function tracer does not follow
the context-info option, so field names are displayed even
if this option is off.
Added check for TRACE_ITER_CONTEXT_INFO trace_flags.
With following commands:
# echo function > ./current_tracer
# echo 0 > options/context-info
# cat trace
This is what it looked like before:
# tracer: function
#
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
add_preempt_count <-schedule
rcu_note_context_switch <-schedule
...
This is what it looks like now:
# tracer: function
#
_raw_spin_unlock_irqrestore <-hrtimer_try_to_cancel
...
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1307113131-10045-4-git-send-email-jolsa@redhat.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Functions print_graph_overhead() and print_graph_duration() displays
data for one field - DURATION.
I merged them into single function print_graph_duration(),
and added a way to display the empty parts of the field.
This way the print_graph_irq() function can use this column to display
the IRQ signs if needed and the DURATION field details stays inside
the print_graph_duration() function.
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1307113131-10045-3-git-send-email-jolsa@redhat.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The display of absolute time and duration fields is based on the
latency field. This was added during the irqsoff/wakeup tracers
graph support changes.
It's causing confusion in what fields will be displayed for the
function_graph tracer itself. So I'm removing this depency, and
adding absolute time and duration fields to the preemptirqsoff
preemptoff irqsoff wakeup tracers.
With following commands:
# echo function_graph > ./current_tracer
# cat trace
This is what it looked like before:
# tracer: function_graph
#
# TIME CPU DURATION FUNCTION CALLS
# | | | | | | | |
0) 0.068 us | } /* page_add_file_rmap */
0) | _raw_spin_unlock() {
...
This is what it looks like now:
# tracer: function_graph
#
# CPU DURATION FUNCTION CALLS
# | | | | | | |
0) 0.068 us | } /* add_preempt_count */
0) 0.993 us | } /* vfsmount_lock_local_lock */
...
For preemptirqsoff preemptoff irqsoff wakeup tracers,
this is what it looked like before:
SNIP
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / _-=> lock-depth
# |||| /
# CPU TASK/PID ||||| DURATION FUNCTION CALLS
# | | | ||||| | | | | | |
1) <idle>-0 | d..1 0.000 us | acpi_idle_enter_simple();
...
This is what it looks like now:
SNIP
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| /
# TIME CPU TASK/PID |||| DURATION FUNCTION CALLS
# | | | | |||| | | | | | |
19.847735 | 1) <idle>-0 | d..1 0.000 us | acpi_idle_enter_simple();
...
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1307113131-10045-2-git-send-email-jolsa@redhat.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Added <linux/atomic.h>,<linux/ktime.h> and Removed <asm/atomic.h>.
Added KERN_DEBUG to printk() functions.
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Paul McQuade <tungstentide@gmail.com>
Link: http://lkml.kernel.org/r/4DE596B4.7030904@gmail.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Add a trace option to disable tracing on free. When this option is
set, a write into the free_buffer file will not only shrink the
ring buffer down to zero, but it will also disable tracing.
Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The proc file entry buffer_size_kb is used to set the size of tracing
buffer. The memory to expand the buffer size is kernel memory. Consider
a use case where tracing is handled by a user space utility, which acts
as a gate keeper for tracing requests. In an OOM condition, tracing is
considered a low priority task and if the utility gets killed the ring
buffer memory cannot be released back to the kernel.
This patch adds a proc file called "free_buffer" whose purpose is to
stop tracing and free up the ring buffer when it is closed.
The user space process can then set the desired size in buffer_size_kb
file and open the fd to the "free_buffer" file. Under OOM condition, if
the process gets killed, the kernel closes the file descriptor. The
release handler stops the tracing and releases the kernel memory
automatically.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Link: http://lkml.kernel.org/r/1308012717-11148-1-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Fix kernel-doc warnings in signal.c:
Warning(kernel/signal.c:2374): No description found for parameter 'nset'
Warning(kernel/signal.c:2374): Excess function parameter 'set' description in 'sys_rt_sigprocmask'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The tracing ring buffer is a group of per-cpu ring buffers where
allocation and logging is done on a per-cpu basis. The events that are
generated on a particular CPU are logged in the corresponding buffer.
This is to provide wait-free writes between CPUs and good NUMA node
locality while accessing the ring buffer.
However, the allocation routines consider NUMA locality only for buffer
page metadata and not for the actual buffer page. This causes the pages
to be allocated on the NUMA node local to the CPU where the allocation
routine is running at the time.
This patch fixes the problem by using a NUMA node specific allocation
routine so that the pages are allocated from a NUMA node local to the
logging CPU.
I tested with the getuid_microbench from autotest. It is a simple binary
that calls getuid() in a loop and measures the average time for the
syscall to complete. The following command was used to test:
$ getuid_microbench 1000000
Compared the numbers found on kernel with and without this patch and
found that logging latency decreases by 30-50 ns/call.
tracing with non-NUMA allocation - 569 ns/call
tracing with NUMA allocation - 512 ns/call
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Link: http://lkml.kernel.org/r/1304470602-20366-1-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
In using syscall tracing by concurrent processes, the wakeup() that is
called in the event commit function causes contention on the spin lock
of the waitqueue. I enabled sys_enter_getuid and sys_exit_getuid
tracepoints, and by running getuid_microbench from autotest in parallel
I found that the contention causes exponential latency increase in the
tracing path.
The autotest binary getuid_microbench calls getuid() in a tight loop for
the given number of iterations and measures the average time required to
complete a single invocation of syscall.
The patch schedules a delayed work after 2 ms once an event commit calls
to wake up the trace wait_queue. This removes the delay caused by
contention on spin lock in wakeup() and amortizes the wakeup() calls
scheduled over the 2 ms period.
In the following example, the script enables the sys_enter_getuid and
sys_exit_getuid tracepoints and runs the getuid_microbench in parallel
with the given number of processes. The output clearly shows the latency
increase caused by contentions.
$ ~/getuid.sh 1
1000000 calls in 0.720974253 s (720.974253 ns/call)
$ ~/getuid.sh 2
1000000 calls in 1.166457554 s (1166.457554 ns/call)
1000000 calls in 1.168933765 s (1168.933765 ns/call)
$ ~/getuid.sh 3
1000000 calls in 1.783827516 s (1783.827516 ns/call)
1000000 calls in 1.795553270 s (1795.553270 ns/call)
1000000 calls in 1.796493376 s (1796.493376 ns/call)
$ ~/getuid.sh 4
1000000 calls in 4.483041796 s (4483.041796 ns/call)
1000000 calls in 4.484165388 s (4484.165388 ns/call)
1000000 calls in 4.484850762 s (4484.850762 ns/call)
1000000 calls in 4.485643576 s (4485.643576 ns/call)
$ ~/getuid.sh 5
1000000 calls in 6.497521653 s (6497.521653 ns/call)
1000000 calls in 6.502000236 s (6502.000236 ns/call)
1000000 calls in 6.501709115 s (6501.709115 ns/call)
1000000 calls in 6.502124100 s (6502.124100 ns/call)
1000000 calls in 6.502936358 s (6502.936358 ns/call)
After the patch, the latencies scale better.
1000000 calls in 0.728720455 s (728.720455 ns/call)
1000000 calls in 0.842782857 s (842.782857 ns/call)
1000000 calls in 0.883803135 s (883.803135 ns/call)
1000000 calls in 0.902077764 s (902.077764 ns/call)
1000000 calls in 0.902838202 s (902.838202 ns/call)
1000000 calls in 0.908896885 s (908.896885 ns/call)
1000000 calls in 0.932523515 s (932.523515 ns/call)
1000000 calls in 0.958009672 s (958.009672 ns/call)
1000000 calls in 0.986188020 s (986.188020 ns/call)
1000000 calls in 0.989771102 s (989.771102 ns/call)
1000000 calls in 0.933518391 s (933.518391 ns/call)
1000000 calls in 0.958897947 s (958.897947 ns/call)
1000000 calls in 1.031038897 s (1031.038897 ns/call)
1000000 calls in 1.089516025 s (1089.516025 ns/call)
1000000 calls in 1.141998347 s (1141.998347 ns/call)
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1305059241-7629-1-git-send-email-vnagarnaik@google.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Commit a26ac2455ffcf3(rcu: move TREE_RCU from softirq to kthread)
introduced performance regression. In an AIM7 test, this commit degraded
performance by about 40%.
The commit runs rcu callbacks in a kthread instead of softirq. We observed
high rate of context switch which is caused by this. Out test system has
64 CPUs and HZ is 1000, so we saw more than 64k context switch per second
which is caused by RCU's per-CPU kthread. A trace showed that most of
the time the RCU per-CPU kthread doesn't actually handle any callbacks,
but instead just does a very small amount of work handling grace periods.
This means that RCU's per-CPU kthreads are making the scheduler do quite
a bit of work in order to allow a very small amount of RCU-related
processing to be done.
Alex Shi's analysis determined that this slowdown is due to lock
contention within the scheduler. Unfortunately, as Peter Zijlstra points
out, the scheduler's real-time semantics require global action, which
means that this contention is inherent in real-time scheduling. (Yes,
perhaps someone will come up with a workaround -- otherwise, -rt is not
going to do well on large SMP systems -- but this patch will work around
this issue in the meantime. And "the meantime" might well be forever.)
This patch therefore re-introduces softirq processing to RCU, but only
for core RCU work. RCU callbacks are still executed in kthread context,
so that only a small amount of RCU work runs in softirq context in the
common case. This should minimize ksoftirqd execution, allowing us to
skip boosting of ksoftirqd for CONFIG_RCU_BOOST=y kernels.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Tested-by: "Alex,Shi" <alex.shi@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Make the functions creating the kthreads wake them up. Leverage the
fact that the per-node and boost kthreads can run anywhere, thus
dispensing with the need to wake them up once the incoming CPU has
gone fully online.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Daniel J Blueman <daniel.blueman@gmail.com>
Steven Rostedt