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Commit 51e0304c authored by Ingo Molnar's avatar Ingo Molnar
Browse files

sched: Implement a gentler fair-sleepers feature 



Add back FAIR_SLEEPERS and GENTLE_FAIR_SLEEPERS.

FAIR_SLEEPERS is the old logic: credit sleepers with their sleep time.

GENTLE_FAIR_SLEEPERS dampens this a bit: 50% of their sleep time gets
credited.

The hope here is to still give the benefits of fair-sleepers logic
(quick wakeups, etc.) while not allow them to have 100% of their
sleep time as if they were running.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 59abf026

kernel/sched_fair.c

+8 −1
Original line number Diff line number Diff line
@@ -711,7 +711,7 @@ 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)) {

		if (sched_feat(FAIR_SLEEPERS)) {

			unsigned long thresh = sysctl_sched_latency;



			/*
@@ -725,6 +725,13 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) 
					 task_of(se)->policy != SCHED_IDLE))

				thresh = calc_delta_fair(thresh, se);



			/*

			 * Halve their sleep time's effect, to allow

			 * for a gentler effect of sleepers:

			 */

			if (sched_feat(GENTLE_FAIR_SLEEPERS))

				thresh >>= 1;



			vruntime -= thresh;

		}

	}

kernel/sched_features.h

+8 −1
Original line number Diff line number Diff line
@@ -3,7 +3,14 @@ 
 * considers the task to be running during that period. This gives it

 * a service deficit on wakeup, allowing it to run sooner.

 */

SCHED_FEAT(NEW_FAIR_SLEEPERS, 0)

SCHED_FEAT(FAIR_SLEEPERS, 1)



/*

 * Only give sleepers 50% of their service deficit. This allows

 * them to run sooner, but does not allow tons of sleepers to

 * rip the spread apart.

 */

SCHED_FEAT(GENTLE_FAIR_SLEEPERS, 1)



/*

 * By not normalizing the sleep time, heavy tasks get an effective