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Commit 58d6c2d7 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched: rt-group: optimize dequeue_rt_stack 



Now that the group hierarchy can have an arbitrary depth the O(n^2) nature
of RT task dequeues will really hurt. Optimize this by providing space to
store the tree path, so we can walk it the other way.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent d19ca308

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -1005,6 +1005,7 @@ struct sched_rt_entity { 
	unsigned long timeout;

	int nr_cpus_allowed;



	struct sched_rt_entity *back;

#ifdef CONFIG_RT_GROUP_SCHED

	struct sched_rt_entity	*parent;

	/* rq on which this entity is (to be) queued: */

kernel/sched_rt.c

+11 −16
Original line number Diff line number Diff line
@@ -479,26 +479,21 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se) 
/*

 * Because the prio of an upper entry depends on the lower

 * entries, we must remove entries top - down.

 *

 * XXX: O(1/2 h^2) because we can only walk up, not down the chain.

 */

static void dequeue_rt_stack(struct task_struct *p)

{

	struct sched_rt_entity *rt_se, *top_se;

	struct sched_rt_entity *rt_se, *back = NULL;



	/*

	 * dequeue all, top - down.

	 */

	do {

	rt_se = &p->rt;

		top_se = NULL;

	for_each_sched_rt_entity(rt_se) {

		rt_se->back = back;

		back = rt_se;

	}



	for (rt_se = back; rt_se; rt_se = rt_se->back) {

		if (on_rt_rq(rt_se))

				top_se = rt_se;

			dequeue_rt_entity(rt_se);

	}

		if (top_se)

			dequeue_rt_entity(top_se);

	} while (top_se);

}



/*