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perf: Do not compute time values unnecessarily

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

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130802191630.GT27162@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2013-08-02 21:16:30 +02:00 committed by Ingo Molnar
parent 948b26b6dd
commit 5ec4c599a5
1 changed files with 4 additions and 4 deletions
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8
kernel/events/core.c
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@ -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.