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Commit e69b0f1b authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Add a few SYNC hint knobs to play with 



Currently we use overlap to weaken the SYNC hint, but allow it to
set the hint as well.

 echo NO_SYNC_WAKEUP > /debug/sched_features
 echo SYNC_MORE > /debug/sched_features

preserves pipe-test behaviour without using the WF_SYNC hint.

Worth playing with on more workloads...

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 63859d4f

kernel/sched_fair.c

+11 −3
Original line number Diff line number Diff line
@@ -1165,9 +1165,17 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) 
	load	  = source_load(prev_cpu, idx);

	this_load = target_load(this_cpu, idx);



	if (sync && (curr->se.avg_overlap > sysctl_sched_migration_cost ||

	if (sync) {

	       if (sched_feat(SYNC_LESS) &&

		   (curr->se.avg_overlap > sysctl_sched_migration_cost ||

		    p->se.avg_overlap > sysctl_sched_migration_cost))

		       sync = 0;

	} else {

		if (sched_feat(SYNC_MORE) &&

		    (curr->se.avg_overlap < sysctl_sched_migration_cost &&

		     p->se.avg_overlap < sysctl_sched_migration_cost))

			sync = 1;

	}



	/*

	 * If sync wakeup then subtract the (maximum possible)

kernel/sched_features.h

+10 −0
Original line number Diff line number Diff line
@@ -62,6 +62,16 @@ SCHED_FEAT(SYNC_WAKEUPS, 1) 
 */

SCHED_FEAT(AFFINE_WAKEUPS, 1)



/*

 * Weaken SYNC hint based on overlap

 */

SCHED_FEAT(SYNC_LESS, 1)



/*

 * Add SYNC hint based on overlap

 */

SCHED_FEAT(SYNC_MORE, 0)



/*

 * Prefer to schedule the task we woke last (assuming it failed

 * wakeup-preemption), since its likely going to consume data we