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ftrace: change buffers to producer consumer 

This patch changes the way the CPU trace buffers are handled.
Instead of always starting from the trace page head, the logic
is changed to a producer consumer logic. This allows for the
buffers to be drained while they are alive.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Steven Rostedt 2008-05-12 21:20:45 +02:00 committed by Thomas Gleixner
parent 1d4db00a5e
commit 93a588f459
2 changed files with 65 additions and 44 deletions
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103
kernel/trace/trace.c
View File

@ -176,10 +176,9 @@ flip_trace(struct trace_array_cpu *tr1, struct trace_array_cpu *tr2)
INIT_LIST_HEAD(&flip_pages);
tr1->trace_current = NULL;
memcpy(&tr1->trace_current_idx, &tr2->trace_current_idx,
memcpy(&tr1->trace_head_idx, &tr2->trace_head_idx,
sizeof(struct trace_array_cpu) -
offsetof(struct trace_array_cpu, trace_current_idx));
offsetof(struct trace_array_cpu, trace_head_idx));
check_pages(tr1);
check_pages(tr2);
@ -228,7 +227,6 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
tracing_reset(max_tr.data[i]);
flip_trace(max_tr.data[cpu], data);
tracing_reset(data);
__update_max_tr(tr, tsk, cpu);
@ -343,9 +341,9 @@ void unregister_tracer(struct tracer *type)
notrace void tracing_reset(struct trace_array_cpu *data)
{
data->trace_idx = 0;
data->trace_current = head_page(data);
data->trace_current_idx = 0;
data->time_offset = 0;
data->trace_head = data->trace_tail = head_page(data);
data->trace_head_idx = 0;
data->trace_tail_idx = 0;
}
#ifdef CONFIG_FTRACE
@ -470,38 +468,65 @@ notrace void tracing_record_cmdline(struct task_struct *tsk)
trace_save_cmdline(tsk);
}
static inline notrace struct list_head *
trace_next_list(struct trace_array_cpu *data, struct list_head *next)
{
/*
* Roundrobin - but skip the head (which is not a real page):
*/
next = next->next;
if (unlikely(next == &data->trace_pages))
next = next->next;
BUG_ON(next == &data->trace_pages);
return next;
}
static inline notrace void *
trace_next_page(struct trace_array_cpu *data, void *addr)
{
struct list_head *next;
struct page *page;
page = virt_to_page(addr);
next = trace_next_list(data, &page->lru);
page = list_entry(next, struct page, lru);
return page_address(page);
}
static inline notrace struct trace_entry *
tracing_get_trace_entry(struct trace_array *tr, struct trace_array_cpu *data)
{
unsigned long idx, idx_next;
struct trace_entry *entry;
struct list_head *next;
struct page *page;
data->trace_idx++;
idx = data->trace_current_idx;
idx = data->trace_head_idx;
idx_next = idx + 1;
BUG_ON(idx * TRACE_ENTRY_SIZE >= PAGE_SIZE);
entry = data->trace_current + idx * TRACE_ENTRY_SIZE;
entry = data->trace_head + idx * TRACE_ENTRY_SIZE;
if (unlikely(idx_next >= ENTRIES_PER_PAGE)) {
page = virt_to_page(data->trace_current);
/*
* Roundrobin - but skip the head (which is not a real page):
*/
next = page->lru.next;
if (unlikely(next == &data->trace_pages))
next = next->next;
BUG_ON(next == &data->trace_pages);
page = list_entry(next, struct page, lru);
data->trace_current = page_address(page);
data->trace_head = trace_next_page(data, data->trace_head);
idx_next = 0;
}
data->trace_current_idx = idx_next;
if (data->trace_head == data->trace_tail &&
idx_next == data->trace_tail_idx) {
/* overrun */
data->trace_tail_idx++;
if (data->trace_tail_idx >= ENTRIES_PER_PAGE) {
data->trace_tail =
trace_next_page(data, data->trace_tail);
data->trace_tail_idx = 0;
}
}
data->trace_head_idx = idx_next;
return entry;
}
@ -571,21 +596,11 @@ trace_entry_idx(struct trace_array *tr, struct trace_array_cpu *data,
return NULL;
if (!iter->next_page[cpu]) {
/*
* Initialize. If the count of elements in
* this buffer is greater than the max entries
* we had an underrun. Which means we looped around.
* We can simply use the current pointer as our
* starting point.
*/
if (data->trace_idx >= tr->entries) {
page = virt_to_page(data->trace_current);
iter->next_page[cpu] = &page->lru;
iter->next_page_idx[cpu] = data->trace_current_idx;
} else {
iter->next_page[cpu] = data->trace_pages.next;
iter->next_page_idx[cpu] = 0;
}
/* Initialize the iterator for this cpu trace buffer */
WARN_ON(!data->trace_tail);
page = virt_to_page(data->trace_tail);
iter->next_page[cpu] = &page->lru;
iter->next_page_idx[cpu] = data->trace_tail_idx;
}
page = list_entry(iter->next_page[cpu], struct page, lru);
@ -593,6 +608,12 @@ trace_entry_idx(struct trace_array *tr, struct trace_array_cpu *data,
array = page_address(page);
/* Still possible to catch up to the tail */
if (iter->next_idx[cpu] && array == data->trace_tail &&
iter->next_page_idx[cpu] == data->trace_tail_idx)
return NULL;
WARN_ON(iter->next_page_idx[cpu] >= ENTRIES_PER_PAGE);
return &array[iter->next_page_idx[cpu]];
}
@ -638,10 +659,8 @@ static void *find_next_entry_inc(struct trace_iterator *iter)
iter->next_page_idx[next_cpu] = 0;
iter->next_page[next_cpu] =
iter->next_page[next_cpu]->next;
if (iter->next_page[next_cpu] == &data->trace_pages)
iter->next_page[next_cpu] =
data->trace_pages.next;
trace_next_list(data, iter->next_page[next_cpu]);
}
}
iter->prev_ent = iter->ent;

6
kernel/trace/trace.h
View File

@ -53,13 +53,15 @@ struct trace_entry {
* the trace, etc.)
*/
struct trace_array_cpu {
void *trace_current;
struct list_head trace_pages;
atomic_t disabled;
cycle_t time_offset;
/* these fields get copied into max-trace: */
unsigned trace_current_idx;
unsigned trace_head_idx;
unsigned trace_tail_idx;
void *trace_head; /* producer */
void *trace_tail; /* consumer */
unsigned long trace_idx;
unsigned long saved_latency;
unsigned long critical_start;