linux-kernel - [tip:sched/core] sched: Optimize branch hint in pick_next_task

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Date:	Tue, 24 Nov 2009 16:56:36 GMT
From:	tip-bot for Tim Blechmann <tim@...ngt.org>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, acme@...hat.com, paulus@...ba.org,
	hpa@...or.com, mingo@...hat.com, a.p.zijlstra@...llo.nl,
	efault@....de, fweisbec@...il.com, tglx@...utronix.de,
	tim@...ngt.org, mingo@...e.hu
Subject: [tip:sched/core] sched: Optimize branch hint in pick_next_task_fair()

Commit-ID:  36ace27e3e60d44ea69ce394b2e45386ae98d9d9
Gitweb:     http://git.kernel.org/tip/36ace27e3e60d44ea69ce394b2e45386ae98d9d9
Author:     Tim Blechmann <tim@...ngt.org>
AuthorDate: Tue, 24 Nov 2009 11:55:45 +0100
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 24 Nov 2009 12:18:12 +0100

sched: Optimize branch hint in pick_next_task_fair()

Branch hint profiling on my nehalem machine showed 90%
incorrect branch hints:

  15728471 158903754  90 pick_next_task_fair
  sched_fair.c    1555

Signed-off-by: Tim Blechmann <tim@...ngt.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Mike Galbraith <efault@....de>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
LKML-Reference: <4B0BBBB1.2050100@...ngt.org>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched_fair.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index f28a267..24086e7 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1704,7 +1704,7 @@ static struct task_struct *pick_next_task_fair(struct rq *rq)
 	struct cfs_rq *cfs_rq = &rq->cfs;
 	struct sched_entity *se;
 
-	if (unlikely(!cfs_rq->nr_running))
+	if (!cfs_rq->nr_running)
 		return NULL;
 
 	do {
--
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