Commit e69c6341 authored Dec 06, 2010 by Steven Rostedt Committed by Steven Rostedt Dec 13, 2010

sched: Remove unlikely() from ttwu_post_activation



The unlikely() used in ttwu_post_activation() tests if the rq->idle_stamp
is set. But since this is for a wakeup, and wakeups happen when tasks
block on IO, and blocking tasks on IO may put the system into idle,
this can actually be a common occurence.

Running the annotated branch profiler on an average desktop running
firefox, evolution, xchat and distcc, the report shows:

 correct incorrect  %        Function             File              Line
 ------- ---------  -        --------             ----              ----
34884862 146110926  80 ttwu_post_activation      sched.c            2309

80% of the time, this unlikely is incorrect. Best not to assume what the
result is, and just remove the branch annotation.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

parent 63f01241

kernel/sched.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2458,7 +2458,7 @@ static inline void ttwu_post_activation(struct task_struct p, struct rq rq,
		if (p->sched_class->task_woken)
		p->sched_class->task_woken(rq, p);

		if (unlikely(rq->idle_stamp)) {
		if (rq->idle_stamp) {
		u64 delta = rq->clock - rq->idle_stamp;
		u64 max = 2*sysctl_sched_migration_cost;

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