* [tip:perf/core] perf: Do not compute time values unnecessarily
[not found] <20130802191630.GT27162@twins.programming.kicks-ass.net>
@ 2013-08-16 18:47 ` tip-bot for Peter Zijlstra
0 siblings, 0 replies; only message in thread
From: tip-bot for Peter Zijlstra @ 2013-08-16 18:47 UTC (permalink / raw)
To: linux-tip-commits; +Cc: linux-kernel, hpa, mingo, peterz, tglx
Commit-ID: 5ec4c599a52362896c3e7c6a31ba6145dca9c6f5
Gitweb: http://git.kernel.org/tip/5ec4c599a52362896c3e7c6a31ba6145dca9c6f5
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 2 Aug 2013 21:16:30 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 16 Aug 2013 17:55:52 +0200
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 <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130802191630.GT27162@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/events/core.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2e675e8..928fae7 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.
^ permalink raw reply [flat|nested] only message in thread