Commit 7abc63b1 authored Oct 18, 2011 by Peter Zijlstra Committed by Ingo Molnar Mar 01, 2012

sched/rt: Do not throttle when PI boosting



When a runqueue has rt_runtime_us = 0 then the only way it can
accumulate rt_time is via PI boosting. That causes the runqueue
to be throttled and replenishing does not change anything due to
rt_runtime_us = 0. So avoid that situation by clearing rt_time and
skip the throttling alltogether.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[ Changelog ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/n/tip-7x70cypsotjb4jvcor3edctk@git.kernel.org


Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 42c62a58

kernel/sched/rt.c

+18 −2

Original line number	Diff line number	Diff line
		@@ -857,8 +857,24 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
		return 0;

		if (rt_rq->rt_time > runtime) {
		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);

		/*
		* Don't actually throttle groups that have no runtime assigned
		* but accrue some time due to boosting.
		*/
		if (likely(rt_b->rt_runtime)) {
		rt_rq->rt_throttled = 1;
		printk_once(KERN_WARNING "sched: RT throttling activated\n");
		} else {
		/*
		* In case we did anyway, make it go away,
		* replenishment is a joke, since it will replenish us
		* with exactly 0 ns.
		*/
		rt_rq->rt_time = 0;
		}

		if (rt_rq_throttled(rt_rq)) {
		sched_rt_rq_dequeue(rt_rq);
		return 1;