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Commit 6bc912b7 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched: SCHED_OTHER vs SCHED_IDLE isolation 



Stronger SCHED_IDLE isolation:

 - no SCHED_IDLE buddies
 - never let SCHED_IDLE preempt on wakeup
 - always preempt SCHED_IDLE on wakeup
 - limit SLEEPER fairness for SCHED_IDLE.

Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent cce7ade8

kernel/sched_fair.c

+22 −8
Original line number Original line Diff line number Diff line
@@ -677,9 +677,13 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) 
			unsigned long thresh = sysctl_sched_latency;

			unsigned long thresh = sysctl_sched_latency;





			/*

			/*

			 * convert the sleeper threshold into virtual time

			 * Convert the sleeper threshold into virtual time.

			 * SCHED_IDLE is a special sub-class.  We care about

			 * fairness only relative to other SCHED_IDLE tasks,

			 * all of which have the same weight.

			 */

			 */

			if (sched_feat(NORMALIZED_SLEEPER))

			if (sched_feat(NORMALIZED_SLEEPER) &&

					task_of(se)->policy != SCHED_IDLE)

				thresh = calc_delta_fair(thresh, se);

				thresh = calc_delta_fair(thresh, se);





			vruntime -= thresh;

			vruntime -= thresh;
@@ -1340,15 +1344,19 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) 




static void set_last_buddy(struct sched_entity *se)

static void set_last_buddy(struct sched_entity *se)

{

{

	if (likely(task_of(se)->policy != SCHED_IDLE)) {

		for_each_sched_entity(se)

		for_each_sched_entity(se)

			cfs_rq_of(se)->last = se;

			cfs_rq_of(se)->last = se;

	}

	}

}





static void set_next_buddy(struct sched_entity *se)

static void set_next_buddy(struct sched_entity *se)

{

{

	if (likely(task_of(se)->policy != SCHED_IDLE)) {

		for_each_sched_entity(se)

		for_each_sched_entity(se)

			cfs_rq_of(se)->next = se;

			cfs_rq_of(se)->next = se;

	}

	}

}





/*

/*

 * Preempt the current task with a newly woken task if needed:

 * Preempt the current task with a newly woken task if needed:
@@ -1393,11 +1401,17 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync) 
		return;

		return;





	/*

	/*

	 * Batch tasks do not preempt (their preemption is driven by

	 * Batch and idle tasks do not preempt (their preemption is driven by

	 * the tick):

	 * the tick):

	 */

	 */

	if (unlikely(p->policy == SCHED_BATCH))

	if (unlikely(p->policy != SCHED_NORMAL))

		return;



	/* Idle tasks are by definition preempted by everybody. */

	if (unlikely(curr->policy == SCHED_IDLE)) {

		resched_task(curr);

		return;

		return;

	}





	if (!sched_feat(WAKEUP_PREEMPT))

	if (!sched_feat(WAKEUP_PREEMPT))

		return;

		return;