Commit 02ffdbc8 authored Nov 20, 2009 by Peter Zijlstra Committed by Ingo Molnar Nov 21, 2009

perf: Optimize perf_event_task_sched_out



Remove an update_context_time() call from the
perf_event_task_sched_out() path and into the branch its needed.

The call was both superfluous, because __perf_event_sched_out()
already does it, and wrong, because it was done without holding
ctx->lock.

Place it in perf_event_sync_stat(), which is the only place it
is needed and which does already hold ctx->lock.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20091120212508.779516394@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent abf4868b

kernel/perf_event.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1120,6 +1120,8 @@ static void perf_event_sync_stat(struct perf_event_context *ctx,
		if (!ctx->nr_stat)
		return;

		update_context_time(ctx);

		event = list_first_entry(&ctx->event_list,
		struct perf_event, event_entry);

		@@ -1163,8 +1165,6 @@ void perf_event_task_sched_out(struct task_struct *task,
		if (likely(!ctx \|\| !cpuctx->task_ctx))
		return;

		update_context_time(ctx);

		rcu_read_lock();
		parent = rcu_dereference(ctx->parent_ctx);
		next_ctx = next->perf_event_ctxp;