Commit e36d8677 authored by Luca Abeni's avatar Luca Abeni Committed by Ingo Molnar
Browse files

sched/deadline: Track the active utilization 



Active utilization is defined as the total utilization of active
(TASK_RUNNING) tasks queued on a runqueue. Hence, it is increased
when a task wakes up and is decreased when a task blocks.

When a task is migrated from CPUi to CPUj, immediately subtract the
task's utilization from CPUi and add it to CPUj. This mechanism is
implemented by modifying the pull and push functions.
Note: this is not fully correct from the theoretical point of view
(the utilization should be removed from CPUi only at the 0 lag
time), a more theoretically sound solution is presented in the
next patches.

Tested-by: default avatarDaniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: default avatarLuca Abeni <luca.abeni@unitn.it>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarJuri Lelli <juri.lelli@arm.com>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/1495138417-6203-2-git-send-email-luca.abeni@santannapisa.it


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1ad3aaf3

kernel/sched/deadline.c

+61 −4
Original line number Diff line number Diff line
@@ -43,6 +43,28 @@ static inline int on_dl_rq(struct sched_dl_entity *dl_se) 
	return !RB_EMPTY_NODE(&dl_se->rb_node);

}



static inline

void add_running_bw(u64 dl_bw, struct dl_rq *dl_rq)

{

	u64 old = dl_rq->running_bw;



	lockdep_assert_held(&(rq_of_dl_rq(dl_rq))->lock);

	dl_rq->running_bw += dl_bw;

	SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */

}



static inline

void sub_running_bw(u64 dl_bw, struct dl_rq *dl_rq)

{

	u64 old = dl_rq->running_bw;



	lockdep_assert_held(&(rq_of_dl_rq(dl_rq))->lock);

	dl_rq->running_bw -= dl_bw;

	SCHED_WARN_ON(dl_rq->running_bw > old); /* underflow */

	if (dl_rq->running_bw > old)

		dl_rq->running_bw = 0;

}



static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)

{

	struct sched_dl_entity *dl_se = &p->dl;
@@ -83,6 +105,8 @@ void init_dl_rq(struct dl_rq *dl_rq) 
#else

	init_dl_bw(&dl_rq->dl_bw);

#endif



	dl_rq->running_bw = 0;

}



#ifdef CONFIG_SMP
@@ -946,10 +970,14 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, 
	 * parameters of the task might need updating. Otherwise,

	 * we want a replenishment of its runtime.

	 */

	if (flags & ENQUEUE_WAKEUP)

	if (flags & ENQUEUE_WAKEUP) {

		struct dl_rq *dl_rq = dl_rq_of_se(dl_se);



		add_running_bw(dl_se->dl_bw, dl_rq);

		update_dl_entity(dl_se, pi_se);

	else if (flags & ENQUEUE_REPLENISH)

	} else if (flags & ENQUEUE_REPLENISH) {

		replenish_dl_entity(dl_se, pi_se);

	}



	__enqueue_dl_entity(dl_se);

}
@@ -998,14 +1026,25 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags) 
	if (!p->dl.dl_throttled && dl_is_constrained(&p->dl))

		dl_check_constrained_dl(&p->dl);



	if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & ENQUEUE_RESTORE)

		add_running_bw(p->dl.dl_bw, &rq->dl);



	/*

	 * If p is throttled, we do nothing. In fact, if it exhausted

	 * If p is throttled, we do not enqueue it. In fact, if it exhausted

	 * its budget it needs a replenishment and, since it now is on

	 * its rq, the bandwidth timer callback (which clearly has not

	 * run yet) will take care of this.

	 */

	if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH))

	 * However, the active utilization does not depend on the fact

	 * that the task is on the runqueue or not (but depends on the

	 * task's state - in GRUB parlance, "inactive" vs "active contending").

	 * In other words, even if a task is throttled its utilization must

	 * be counted in the active utilization; hence, we need to call

	 * add_running_bw().

	 */

	if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH)) {

		add_running_bw(p->dl.dl_bw, &rq->dl);

		return;

	}



	enqueue_dl_entity(&p->dl, pi_se, flags);
@@ -1023,6 +1062,20 @@ static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags) 
{

	update_curr_dl(rq);

	__dequeue_task_dl(rq, p, flags);



	if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & DEQUEUE_SAVE)

		sub_running_bw(p->dl.dl_bw, &rq->dl);



	/*

	 * This check allows to decrease the active utilization in two cases:

	 * when the task blocks and when it is terminating

	 * (p->state == TASK_DEAD). We can handle the two cases in the same

	 * way, because from GRUB's point of view the same thing is happening

	 * (the task moves from "active contending" to "active non contending"

	 * or "inactive")

	 */

	if (flags & DEQUEUE_SLEEP)

		sub_running_bw(p->dl.dl_bw, &rq->dl);

}



/*
@@ -1551,7 +1604,9 @@ retry: 
	}



	deactivate_task(rq, next_task, 0);

	sub_running_bw(next_task->dl.dl_bw, &rq->dl);

	set_task_cpu(next_task, later_rq->cpu);

	add_running_bw(next_task->dl.dl_bw, &later_rq->dl);

	activate_task(later_rq, next_task, 0);

	ret = 1;
@@ -1639,7 +1694,9 @@ static void pull_dl_task(struct rq *this_rq) 
			resched = true;



			deactivate_task(src_rq, p, 0);

			sub_running_bw(p->dl.dl_bw, &src_rq->dl);

			set_task_cpu(p, this_cpu);

			add_running_bw(p->dl.dl_bw, &this_rq->dl);

			activate_task(this_rq, p, 0);

			dmin = p->dl.deadline;

kernel/sched/sched.h

+6 −0
Original line number Diff line number Diff line
@@ -558,6 +558,12 @@ struct dl_rq { 
#else

	struct dl_bw dl_bw;

#endif

	/*

	 * "Active utilization" for this runqueue: increased when a

	 * task wakes up (becomes TASK_RUNNING) and decreased when a

	 * task blocks

	 */

	u64 running_bw;

};



#ifdef CONFIG_SMP

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