Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-11-28 15:11:31 +00:00
Code Issues Packages Projects Releases Wiki Activity

ftrace: change buffers to producer consumer

Browse Source 
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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;