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Commit b42e0c41 authored by Mike Galbraith's avatar Mike Galbraith Committed by Ingo Molnar
Browse files

sched: Remove avg_wakeup 



Testing the load which led to this heuristic (nfs4 kbuild) shows that it has
outlived it's usefullness.  With intervening load balancing changes, I cannot
see any difference with/without, so recover there fastpath cycles.

Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301062.6785.29.camel@marge.simson.net>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 39c0cbe2

include/linux/sched.h

+0 −3
Original line number Diff line number Diff line
@@ -1185,9 +1185,6 @@ struct sched_entity { 


	u64			nr_migrations;



	u64			start_runtime;

	u64			avg_wakeup;



#ifdef CONFIG_SCHEDSTATS

	struct sched_statistics statistics;

#endif

kernel/sched.c

+4 −22
Original line number Diff line number Diff line
@@ -1880,9 +1880,6 @@ static void update_avg(u64 *avg, u64 sample) 
static void

enqueue_task(struct rq *rq, struct task_struct *p, int wakeup, bool head)

{

	if (wakeup)

		p->se.start_runtime = p->se.sum_exec_runtime;



	sched_info_queued(p);

	p->sched_class->enqueue_task(rq, p, wakeup, head);

	p->se.on_rq = 1;
@@ -1890,17 +1887,11 @@ enqueue_task(struct rq *rq, struct task_struct *p, int wakeup, bool head) 


static void dequeue_task(struct rq *rq, struct task_struct *p, int sleep)

{

	if (sleep) {

		if (p->se.last_wakeup) {

	if (sleep && p->se.last_wakeup) {

		update_avg(&p->se.avg_overlap,

			p->se.sum_exec_runtime - p->se.last_wakeup);

		p->se.last_wakeup = 0;

		} else {

			update_avg(&p->se.avg_wakeup,

				sysctl_sched_wakeup_granularity);

		}

	}



	sched_info_dequeued(p);

	p->sched_class->dequeue_task(rq, p, sleep);

	p->se.on_rq = 0;
@@ -2466,13 +2457,6 @@ out_activate: 
	 */

	if (!in_interrupt()) {

		struct sched_entity *se = &current->se;

		u64 sample = se->sum_exec_runtime;



		if (se->last_wakeup)

			sample -= se->last_wakeup;

		else

			sample -= se->start_runtime;

		update_avg(&se->avg_wakeup, sample);



		se->last_wakeup = se->sum_exec_runtime;

	}
@@ -2540,8 +2524,6 @@ static void __sched_fork(struct task_struct *p) 
	p->se.nr_migrations		= 0;

	p->se.last_wakeup		= 0;

	p->se.avg_overlap		= 0;

	p->se.start_runtime		= 0;

	p->se.avg_wakeup		= sysctl_sched_wakeup_granularity;



#ifdef CONFIG_SCHEDSTATS

	memset(&p->se.statistics, 0, sizeof(p->se.statistics));

kernel/sched_debug.c

+0 −1
Original line number Diff line number Diff line
@@ -408,7 +408,6 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m) 
	PN(se.vruntime);

	PN(se.sum_exec_runtime);

	PN(se.avg_overlap);

	PN(se.avg_wakeup);



	nr_switches = p->nvcsw + p->nivcsw;

kernel/sched_fair.c

+0 −31
Original line number Diff line number Diff line
@@ -1592,42 +1592,11 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag 
}

#endif /* CONFIG_SMP */



/*

 * Adaptive granularity

 *

 * se->avg_wakeup gives the average time a task runs until it does a wakeup,

 * with the limit of wakeup_gran -- when it never does a wakeup.

 *

 * So the smaller avg_wakeup is the faster we want this task to preempt,

 * but we don't want to treat the preemptee unfairly and therefore allow it

 * to run for at least the amount of time we'd like to run.

 *

 * NOTE: we use 2*avg_wakeup to increase the probability of actually doing one

 *

 * NOTE: we use *nr_running to scale with load, this nicely matches the

 *       degrading latency on load.

 */

static unsigned long

adaptive_gran(struct sched_entity *curr, struct sched_entity *se)

{

	u64 this_run = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;

	u64 expected_wakeup = 2*se->avg_wakeup * cfs_rq_of(se)->nr_running;

	u64 gran = 0;



	if (this_run < expected_wakeup)

		gran = expected_wakeup - this_run;



	return min_t(s64, gran, sysctl_sched_wakeup_granularity);

}



static unsigned long

wakeup_gran(struct sched_entity *curr, struct sched_entity *se)

{

	unsigned long gran = sysctl_sched_wakeup_granularity;



	if (cfs_rq_of(curr)->curr && sched_feat(ADAPTIVE_GRAN))

		gran = adaptive_gran(curr, se);



	/*

	 * Since its curr running now, convert the gran from real-time

	 * to virtual-time in his units.

kernel/sched_features.h

+0 −6
Original line number Diff line number Diff line
@@ -30,12 +30,6 @@ SCHED_FEAT(START_DEBIT, 1) 
 */

SCHED_FEAT(WAKEUP_PREEMPT, 1)



/*

 * Compute wakeup_gran based on task behaviour, clipped to

 *  [0, sched_wakeup_gran_ns]

 */

SCHED_FEAT(ADAPTIVE_GRAN, 1)



/*

 * When converting the wakeup granularity to virtual time, do it such

 * that heavier tasks preempting a lighter task have an edge.