From: Peter Zijlstra Date: Fri, 2 Aug 2013 19:16:30 +0000 (+0200) Subject: perf: Do not compute time values unnecessarily X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=5ec4c599a52362896c3e7c6a31ba6145dca9c6f5;p=openwrt%2Fstaging%2Fblogic.git 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: Peter Zijlstra Link: http://lkml.kernel.org/r/20130802191630.GT27162@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- diff --git a/kernel/events/core.c b/kernel/events/core.c index 2e675e830976..928fae7ca8c7 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -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.