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authorPeter Zijlstra <peterz@infradead.org>2016-02-24 18:45:47 +0100
committerIngo Molnar <mingo@kernel.org>2016-02-25 08:42:34 +0100
commit3cbaa59069677920186dcf502632ca1df4329f80 (patch)
tree13ec3912e610022413592d793fa27704b338ab64 /kernel
parentperf: Cure event->pending_disable race (diff)
downloadlinux-3cbaa59069677920186dcf502632ca1df4329f80.tar.xz
linux-3cbaa59069677920186dcf502632ca1df4329f80.zip
perf: Fix ctx time tracking by introducing EVENT_TIME
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c42
1 files changed, 30 insertions, 12 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index de14b67a3b0b..75bde93eb76f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -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);
}