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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>
This commit is contained in:
Steven Rostedt 2010-12-06 17:10:31 -05:00 committed by Steven Rostedt
parent 63f0124117
commit e69c634190
1 changed files with 1 additions and 1 deletions
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2
kernel/sched.c
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@ -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;