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Commit 2087a1ad authored by Gregory Haskins's avatar Gregory Haskins Committed by Ingo Molnar
Browse files

sched: add avg-overlap support to RT tasks 



We have the notion of tracking process-coupling (a.k.a. buddy-wake) via
the p->se.last_wake / p->se.avg_overlap facilities, but it is only used
for cfs to cfs interactions.  There is no reason why an rt to cfs
interaction cannot share in establishing a relationhip in a similar
manner.

Because PREEMPT_RT runs many kernel threads as FIFO priority, we often
times have heavy interaction between RT threads waking CFS applications.
This patch offers a substantial boost (50-60%+) in perfomance under those
circumstances.

Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
Cc: npiggin@suse.de
Cc: rostedt@goodmis.org
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c4acb2c0

kernel/sched.c

+14 −0
Original line number Diff line number Diff line
@@ -1693,6 +1693,12 @@ static void set_load_weight(struct task_struct *p) 
	p->se.load.inv_weight = prio_to_wmult[p->static_prio - MAX_RT_PRIO];

}



static void update_avg(u64 *avg, u64 sample)

{

	s64 diff = sample - *avg;

	*avg += diff >> 3;

}



static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup)

{

	sched_info_queued(p);
@@ -1702,6 +1708,12 @@ static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup) 


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

{

	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;

	}



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

	p->se.on_rq = 0;

}
@@ -2313,6 +2325,8 @@ out_running: 
		p->sched_class->task_wake_up(rq, p);

#endif

out:

	current->se.last_wakeup = current->se.sum_exec_runtime;



	task_rq_unlock(rq, &flags);



	return success;

kernel/sched_fair.c

+2 −19
Original line number Diff line number Diff line
@@ -726,21 +726,6 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup) 
		__enqueue_entity(cfs_rq, se);

}



static void update_avg(u64 *avg, u64 sample)

{

	s64 diff = sample - *avg;

	*avg += diff >> 3;

}



static void update_avg_stats(struct cfs_rq *cfs_rq, struct sched_entity *se)

{

	if (!se->last_wakeup)

		return;



	update_avg(&se->avg_overlap, se->sum_exec_runtime - se->last_wakeup);

	se->last_wakeup = 0;

}



static void

dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)

{
@@ -751,7 +736,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep) 


	update_stats_dequeue(cfs_rq, se);

	if (sleep) {

		update_avg_stats(cfs_rq, se);

#ifdef CONFIG_SCHEDSTATS

		if (entity_is_task(se)) {

			struct task_struct *tsk = task_of(se);
@@ -1196,7 +1180,7 @@ wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq, 
	 * a reasonable amount of time then attract this newly

	 * woken task:

	 */

	if (sync && balanced && curr->sched_class == &fair_sched_class) {

	if (sync && balanced) {

		if (curr->se.avg_overlap < sysctl_sched_migration_cost &&

		    p->se.avg_overlap < sysctl_sched_migration_cost)

			return 1;
@@ -1359,7 +1343,6 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p) 
		return;

	}



	se->last_wakeup = se->sum_exec_runtime;

	if (unlikely(se == pse))

		return;