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perf_events: Improve task_sched_in()

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This patch is an optimization in perf_event_task_sched_in() to avoid
scheduling the events twice in a row.

Without it, the perf_disable()/perf_enable() pair is invoked twice,
thereby pinned events counts while scheduling flexible events and we go
throuh hw_perf_enable() twice.

By encapsulating, the whole sequence into perf_disable()/perf_enable() we
ensure, hw_perf_enable() is going to be invoked only once because of the
refcount protection.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268288765-5326-1-git-send-email-eranian@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
eranian@google.com 2010-03-10 22:26:05 -08:00 committed by Ingo Molnar
parent caa0142d84
commit 9b33fa6ba0
1 changed files with 4 additions and 0 deletions
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4
kernel/perf_event.c
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@ -1368,6 +1368,8 @@ void perf_event_task_sched_in(struct task_struct *task)
if (cpuctx->task_ctx == ctx)
return;
perf_disable();
/*
* We want to keep the following priority order:
* cpu pinned (that don't need to move), task pinned,
@ -1380,6 +1382,8 @@ void perf_event_task_sched_in(struct task_struct *task)
ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE);
cpuctx->task_ctx = ctx;
perf_enable();
}
#define MAX_INTERRUPTS (~0ULL)