linux-kernel - [PATCH] sched/rt: Don't active rt throtting when no running cfs task

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Date:   Tue, 16 Jun 2020 20:37:29 +0800
From:   Lichao Liu <liulichao@...ngson.cn>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org
Cc:     dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, linux-kernel@...r.kernel.org,
        Lichao Liu <liulichao@...ngson.cn>
Subject: [PATCH] sched/rt: Don't active rt throtting when no running cfs task

Active rt throtting will dequeue rt_rq from rq at least 50ms,
When there is no running cfs task, do we still active it?

Signed-off-by: Lichao Liu <liulichao@...ngson.cn>
---
 kernel/sched/rt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index df11d88c9895..d6524347cea0 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -961,12 +961,13 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 
 	if (rt_rq->rt_time > runtime) {
 		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
+		struct rq *rq = rq_of_rt_rq(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)) {
+		if (likely(rt_b->rt_runtime) && rq->cfs.nr_running > 0) {
 			rt_rq->rt_throttled = 1;
 			printk_deferred_once("sched: RT throttling activated\n");
 		} else {
-- 
2.25.1