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perf: Fix ctx time tracking by introducing EVENT_TIME

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Currently any ctx_sched_in() call will re-start the ctx time tracking,
this means that calls like:

	ctx_sched_in(.event_type = EVENT_PINNED);
	ctx_sched_in(.event_type = EVENT_FLEXIBLE);

will have a hole in their ctx time tracking. This is likely harmless
but can confuse things a little. By adding EVENT_TIME, we can have the
first ctx_sched_in() (is_active: 0 -> !0) start the time and any
further ctx_sched_in() will leave the timestamps alone.

Secondly, this allows for an early disable like:

	ctx_sched_out(.event_type = EVENT_TIME);

which would update the ctx time (if the ctx is active) and any further
calls to ctx_sched_out() would not further modify the ctx time.

For ctx_sched_in() any 0 -> !0 transition will automatically include
EVENT_TIME.

For ctx_sched_out(), any transition that clears EVENT_ALL will
automatically clear EVENT_TIME.

These two rules ensure that under normal circumstances we need not
bother with EVENT_TIME and get natural ctx time behaviour.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174948.100446561@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2016-02-24 18:45:47 +01:00 committed by Ingo Molnar
parent 28a967c3a2
commit 3cbaa59069
1 changed files with 30 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
kernel/events/core.c
View File

@ -314,6 +314,7 @@ again:
enum event_type_t {
EVENT_FLEXIBLE = 0x1,
EVENT_PINNED = 0x2,
EVENT_TIME = 0x4,
EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
};
@ -1294,16 +1295,18 @@ static u64 perf_event_time(struct perf_event *event)
/*
* Update the total_time_enabled and total_time_running fields for a event.
* The caller of this function needs to hold the ctx->lock.
*/
static void update_event_times(struct perf_event *event)
{
struct perf_event_context *ctx = event->ctx;
u64 run_end;
lockdep_assert_held(&ctx->lock);
if (event->state < PERF_EVENT_STATE_INACTIVE ||
event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
return;
/*
* in cgroup mode, time_enabled represents
* the time the event was enabled AND active
@ -2349,24 +2352,33 @@ static void ctx_sched_out(struct perf_event_context *ctx,
}
ctx->is_active &= ~event_type;
if (!(ctx->is_active & EVENT_ALL))
ctx->is_active = 0;
if (ctx->task) {
WARN_ON_ONCE(cpuctx->task_ctx != ctx);
if (!ctx->is_active)
cpuctx->task_ctx = NULL;
}
update_context_time(ctx);
update_cgrp_time_from_cpuctx(cpuctx);
if (!ctx->nr_active)
is_active ^= ctx->is_active; /* changed bits */
if (is_active & EVENT_TIME) {
/* update (and stop) ctx time */
update_context_time(ctx);
update_cgrp_time_from_cpuctx(cpuctx);
}
if (!ctx->nr_active || !(is_active & EVENT_ALL))
return;
perf_pmu_disable(ctx->pmu);
if ((is_active & EVENT_PINNED) && (event_type & EVENT_PINNED)) {
if (is_active & EVENT_PINNED) {
list_for_each_entry(event, &ctx->pinned_groups, group_entry)
group_sched_out(event, cpuctx, ctx);
}
if ((is_active & EVENT_FLEXIBLE) && (event_type & EVENT_FLEXIBLE)) {
if (is_active & EVENT_FLEXIBLE) {
list_for_each_entry(event, &ctx->flexible_groups, group_entry)
group_sched_out(event, cpuctx, ctx);
}
@ -2740,7 +2752,7 @@ ctx_sched_in(struct perf_event_context *ctx,
if (likely(!ctx->nr_events))
return;
ctx->is_active |= event_type;
ctx->is_active |= (event_type | EVENT_TIME);
if (ctx->task) {
if (!is_active)
cpuctx->task_ctx = ctx;
@ -2748,18 +2760,24 @@ ctx_sched_in(struct perf_event_context *ctx,
WARN_ON_ONCE(cpuctx->task_ctx != ctx);
}
now = perf_clock();
ctx->timestamp = now;
perf_cgroup_set_timestamp(task, ctx);
is_active ^= ctx->is_active; /* changed bits */
if (is_active & EVENT_TIME) {
/* start ctx time */
now = perf_clock();
ctx->timestamp = now;
perf_cgroup_set_timestamp(task, ctx);
}
/*
* First go through the list and put on any pinned groups
* in order to give them the best chance of going on.
*/
if (!(is_active & EVENT_PINNED) && (event_type & EVENT_PINNED))
if (is_active & EVENT_PINNED)
ctx_pinned_sched_in(ctx, cpuctx);
/* Then walk through the lower prio flexible groups */
if (!(is_active & EVENT_FLEXIBLE) && (event_type & EVENT_FLEXIBLE))
if (is_active & EVENT_FLEXIBLE)
ctx_flexible_sched_in(ctx, cpuctx);
}