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Commit 5ec4c599 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf: Do not compute time values unnecessarily 



We should not be calling calc_timer_values() for events that do not actually
have an mmap()'ed userpage.

Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130802191630.GT27162@twins.programming.kicks-ass.net


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 948b26b6

kernel/events/core.c

+4 −4
Original line number Diff line number Diff line
@@ -3670,6 +3670,10 @@ void perf_event_update_userpage(struct perf_event *event) 
	u64 enabled, running, now;



	rcu_read_lock();

	rb = rcu_dereference(event->rb);

	if (!rb)

		goto unlock;



	/*

	 * compute total_time_enabled, total_time_running

	 * based on snapshot values taken when the event
@@ -3680,12 +3684,8 @@ void perf_event_update_userpage(struct perf_event *event) 
	 * NMI context

	 */

	calc_timer_values(event, &now, &enabled, &running);

	rb = rcu_dereference(event->rb);

	if (!rb)

		goto unlock;



	userpg = rb->user_page;



	/*

	 * Disable preemption so as to not let the corresponding user-space

	 * spin too long if we get preempted.