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Commit 67e9fb2a authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: add vslice 



add vslice: the load-dependent "virtual slice" a task should
run ideally, so that the observed latency stays within the
sched_latency window.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 1aa4731e

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -908,6 +908,7 @@ struct sched_entity { 
	u64			sum_exec_runtime;

	u64			vruntime;

	u64			prev_sum_exec_runtime;

	u64			last_min_vruntime;



#ifdef CONFIG_SCHEDSTATS

	u64			wait_start;

kernel/sched.c

+2 −0
Original line number Diff line number Diff line
@@ -1615,6 +1615,7 @@ static void __sched_fork(struct task_struct *p) 
	p->se.exec_start		= 0;

	p->se.sum_exec_runtime		= 0;

	p->se.prev_sum_exec_runtime	= 0;

	p->se.last_min_vruntime		= 0;



#ifdef CONFIG_SCHEDSTATS

	p->se.wait_start		= 0;
@@ -6495,6 +6496,7 @@ static inline void init_cfs_rq(struct cfs_rq *cfs_rq, struct rq *rq) 
#ifdef CONFIG_FAIR_GROUP_SCHED

	cfs_rq->rq = rq;

#endif

	cfs_rq->min_vruntime = (u64)(-(1LL << 20));

}



void __init sched_init(void)

kernel/sched_fair.c

+29 −15
Original line number Diff line number Diff line
@@ -243,6 +243,15 @@ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) 
	return period;

}



static u64 __sched_vslice(unsigned long nr_running)

{

	u64 period = __sched_period(nr_running);



	do_div(period, nr_running);



	return period;

}



/*

 * Update the current task's runtime statistics. Skip current tasks that

 * are not in our scheduling class.
@@ -441,32 +450,33 @@ static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) 
static void

place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)

{

	u64 min_runtime, latency;

	u64 vruntime;



	min_runtime = cfs_rq->min_vruntime;

	vruntime = cfs_rq->min_vruntime;



	if (sched_feat(USE_TREE_AVG)) {

		struct sched_entity *last = __pick_last_entity(cfs_rq);

		if (last) {

			min_runtime = __pick_next_entity(cfs_rq)->vruntime;

			min_runtime += last->vruntime;

			min_runtime >>= 1;

			vruntime += last->vruntime;

			vruntime >>= 1;

		}

	} else if (sched_feat(APPROX_AVG))

		min_runtime += sysctl_sched_latency/2;

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

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



	if (initial && sched_feat(START_DEBIT))

		min_runtime += sched_slice(cfs_rq, se);

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



	if (!initial && sched_feat(NEW_FAIR_SLEEPERS)) {

		latency = sysctl_sched_latency;

		if (min_runtime > latency)

			min_runtime -= latency;

		s64 latency = cfs_rq->min_vruntime - se->last_min_vruntime;

		if (latency < 0 || !cfs_rq->nr_running)

			latency = 0;

		else

			min_runtime = 0;

			latency = min_t(s64, latency, sysctl_sched_latency);

		vruntime -= latency;

	}



	se->vruntime = max(se->vruntime, min_runtime);

	se->vruntime = vruntime;



}



static void
@@ -478,6 +488,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup) 
	update_curr(cfs_rq);



	if (wakeup) {

		/* se->vruntime += cfs_rq->min_vruntime; */

		place_entity(cfs_rq, se, 0);

		enqueue_sleeper(cfs_rq, se);

	}
@@ -492,8 +503,8 @@ static void 
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)

{

	update_stats_dequeue(cfs_rq, se);

#ifdef CONFIG_SCHEDSTATS

	if (sleep) {

#ifdef CONFIG_SCHEDSTATS

		if (entity_is_task(se)) {

			struct task_struct *tsk = task_of(se);
@@ -502,8 +513,11 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep) 
			if (tsk->state & TASK_UNINTERRUPTIBLE)

				se->block_start = rq_of(cfs_rq)->clock;

		}

	}

#endif

		/* se->vruntime = entity_key(cfs_rq, se); */

		se->last_min_vruntime = cfs_rq->min_vruntime;

	}



	if (se != cfs_rq->curr)

		__dequeue_entity(cfs_rq, se);

	account_entity_dequeue(cfs_rq, se);