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sched: fix high wake up latencies with FAIR_USER_SCHED 

The reason why we are getting better wakeup latencies for
!FAIR_USER_SCHED is because of this snippet of code in place_entity():

	if (!initial) {
		/* sleeps upto a single latency don't count. */
		if (sched_feat(NEW_FAIR_SLEEPERS) && entity_is_task(se))
						     ^^^^^^^^^^^^^^^^^^
			vruntime -= sysctl_sched_latency;

		/* ensure we never gain time by being placed backwards. */
		vruntime = max_vruntime(se->vruntime, vruntime);
	}

NEW_FAIR_SLEEPERS feature gives credit for sleeping only to tasks and
not group-level entities. With the patch attached, I could see that
wakeup latencies with FAIR_USER_SCHED are restored to the same level as
!FAIR_USER_SCHED.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Srivatsa Vaddagiri 2008-01-31 22:45:22 +01:00 committed by Ingo Molnar
parent 095031052b
commit 296825cbe1
1 changed files with 1 additions and 1 deletions
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2
kernel/sched_fair.c
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@ -520,7 +520,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
if (!initial) {
/* sleeps upto a single latency don't count. */
if (sched_feat(NEW_FAIR_SLEEPERS) && entity_is_task(se))
if (sched_feat(NEW_FAIR_SLEEPERS))
vruntime -= sysctl_sched_latency;
/* ensure we never gain time by being placed backwards. */