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Commit 647e7cac authored by Ingo Molnar's avatar Ingo Molnar
Browse files

sched: vslice fixups for non-0 nice levels 



Make vslice accurate wrt nice levels, and add some comments
while we're at it.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 3a252015

kernel/sched_fair.c

+40 −13
Original line number Original line Diff line number Diff line
@@ -217,6 +217,15 @@ static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) 
 * Scheduling class statistics methods:

 * Scheduling class statistics methods:

 */

 */







/*

 * The idea is to set a period in which each task runs once.

 *

 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch

 * this period because otherwise the slices get too small.

 *

 * p = (nr <= nl) ? l : l*nr/nl

 */

static u64 __sched_period(unsigned long nr_running)

static u64 __sched_period(unsigned long nr_running)

{

{

	u64 period = sysctl_sched_latency;

	u64 period = sysctl_sched_latency;
@@ -230,27 +239,45 @@ static u64 __sched_period(unsigned long nr_running) 
	return period;

	return period;

}

}





/*

 * We calculate the wall-time slice from the period by taking a part

 * proportional to the weight.

 *

 * s = p*w/rw

 */

static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)

static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)

{

{

	u64 period = __sched_period(cfs_rq->nr_running);

	u64 slice = __sched_period(cfs_rq->nr_running);





	period *= se->load.weight;

	slice *= se->load.weight;

	do_div(period, cfs_rq->load.weight);

	do_div(slice, cfs_rq->load.weight);





	return period;

	return slice;

}

}





static u64 __sched_vslice(unsigned long nr_running)

/*

 * We calculate the vruntime slice.

 *

 * vs = s/w = p/rw

 */

static u64 __sched_vslice(unsigned long rq_weight, unsigned long nr_running)

{

{

	unsigned long period = sysctl_sched_latency;

	u64 vslice = __sched_period(nr_running);

	unsigned long nr_latency = sysctl_sched_nr_latency;





	if (unlikely(nr_running > nr_latency))

	do_div(vslice, rq_weight);

		nr_running = nr_latency;





	period /= nr_running;

	return vslice;

}





	return (u64)period;

static u64 sched_vslice(struct cfs_rq *cfs_rq)

{

	return __sched_vslice(cfs_rq->load.weight, cfs_rq->nr_running);

}



static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)

{

	return __sched_vslice(cfs_rq->load.weight + se->load.weight,

			cfs_rq->nr_running + 1);

}

}





/*

/*
@@ -469,10 +496,10 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) 
			vruntime >>= 1;

			vruntime >>= 1;

		}

		}

	} else if (sched_feat(APPROX_AVG) && cfs_rq->nr_running)

	} else if (sched_feat(APPROX_AVG) && cfs_rq->nr_running)

		vruntime += __sched_vslice(cfs_rq->nr_running)/2;

		vruntime += sched_vslice(cfs_rq)/2;





	if (initial && sched_feat(START_DEBIT))

	if (initial && sched_feat(START_DEBIT))

		vruntime += __sched_vslice(cfs_rq->nr_running + 1);

		vruntime += sched_vslice_add(cfs_rq, se);





	if (!initial) {

	if (!initial) {

		if (sched_feat(NEW_FAIR_SLEEPERS))

		if (sched_feat(NEW_FAIR_SLEEPERS))