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Subject: [patchlet] sched: minor fast-path overhead reduction
From: Mike Galbraith <efault@gmx.de>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>
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Date: Fri, 17 Oct 2008 15:33:21 +0200
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Greetings,

103638d added a bit of avoidable overhead to the fast-path.

Use sysctl_sched_min_granularity instead of sched_slice() to restrict buddy wakeups.

Signed-off-by: Mike Galbraith <efault@gmx.de>
 
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 18fd171..6708493 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -747,7 +747,7 @@ pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se)
 	struct rq *rq = rq_of(cfs_rq);
 	u64 pair_slice = rq->clock - cfs_rq->pair_start;
 
-	if (!cfs_rq->next || pair_slice > sched_slice(cfs_rq, cfs_rq->next)) {
+	if (!cfs_rq->next || pair_slice > sysctl_sched_min_granularity) {
 		cfs_rq->pair_start = rq->clock;
 		return se;
 	}