Commit 781773e3 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

sched/fair: Implement ENQUEUE_DELAYED 



Doing a wakeup on a delayed dequeue task is about as simple as it
sounds -- remove the delayed mark and enjoy the fact it was actually
still on the runqueue.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarValentin Schneider <vschneid@redhat.com>
Tested-by: default avatarValentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105029.888107381@infradead.org
parent f12e1488

kernel/sched/fair.c

+31 −2
Original line number Diff line number Diff line
@@ -5289,6 +5289,9 @@ static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq); 


static inline bool cfs_bandwidth_used(void);



static void

requeue_delayed_entity(struct sched_entity *se);



static void

enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)

{
@@ -5922,8 +5925,10 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) 
	for_each_sched_entity(se) {

		struct cfs_rq *qcfs_rq = cfs_rq_of(se);



		if (se->on_rq)

		if (se->on_rq) {

			SCHED_WARN_ON(se->sched_delayed);

			break;

		}

		enqueue_entity(qcfs_rq, se, ENQUEUE_WAKEUP);



		if (cfs_rq_is_idle(group_cfs_rq(se)))
@@ -6773,6 +6778,22 @@ static int sched_idle_cpu(int cpu) 
}

#endif



static void

requeue_delayed_entity(struct sched_entity *se)

{

	struct cfs_rq *cfs_rq = cfs_rq_of(se);



	/*

	 * se->sched_delayed should imply: se->on_rq == 1.

	 * Because a delayed entity is one that is still on

	 * the runqueue competing until elegibility.

	 */

	SCHED_WARN_ON(!se->sched_delayed);

	SCHED_WARN_ON(!se->on_rq);



	se->sched_delayed = 0;

}



/*

 * The enqueue_task method is called before nr_running is

 * increased. Here we update the fair scheduling stats and
@@ -6787,6 +6808,11 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
	int task_new = !(flags & ENQUEUE_WAKEUP);

	int rq_h_nr_running = rq->cfs.h_nr_running;



	if (flags & ENQUEUE_DELAYED) {

		requeue_delayed_entity(se);

		return;

	}



	/*

	 * The code below (indirectly) updates schedutil which looks at

	 * the cfs_rq utilization to select a frequency.
@@ -6804,8 +6830,11 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);



	for_each_sched_entity(se) {

		if (se->on_rq)

		if (se->on_rq) {

			if (se->sched_delayed)

				requeue_delayed_entity(se);

			break;

		}

		cfs_rq = cfs_rq_of(se);

		enqueue_entity(cfs_rq, se, flags);