linux-kernel - [PATCH 4/4 v4] sched/nohz: monitor rt utilization

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Date:   Fri, 16 Mar 2018 12:25:41 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, rjw@...ysocki.net
Cc:     juri.lelli@...hat.com, dietmar.eggemann@....com,
        Morten.Rasmussen@....com, viresh.kumar@...aro.org,
        valentin.schneider@....com,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 4/4 v4] sched/nohz: monitor rt utilization

Take into account rt's utilization when deciding to stop periodic update

Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
---
 kernel/sched/fair.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 60e3c4b..3f00e03 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7131,6 +7131,14 @@ static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
 	return false;
 }
 
+static inline bool rt_rq_has_blocked(struct rt_rq *rt_rq)
+{
+	if (rt_rq->avg.util_avg)
+		return true;
+
+	return false;
+}
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
 static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
@@ -7191,6 +7199,9 @@ static void update_blocked_averages(int cpu)
 			done = false;
 	}
 	update_rt_rq_load_avg(rq_clock_task(rq), cpu, &rq->rt, 0);
+	/* Don't need periodic decay once load/util_avg are null */
+	if (rt_rq_has_blocked(&rq->rt))
+		done = false;
 
 #ifdef CONFIG_NO_HZ_COMMON
 	rq->last_blocked_load_update_tick = jiffies;
@@ -7259,7 +7270,7 @@ static inline void update_blocked_averages(int cpu)
 	update_rt_rq_load_avg(rq_clock_task(rq), cpu, &rq->rt, 0);
 #ifdef CONFIG_NO_HZ_COMMON
 	rq->last_blocked_load_update_tick = jiffies;
-	if (!cfs_rq_has_blocked(cfs_rq))
+	if (!cfs_rq_has_blocked(cfs_rq) && !rt_rq_has_blocked(&rq->rt))
 		rq->has_blocked_load = 0;
 #endif
 	rq_unlock_irqrestore(rq, &rf);
-- 
2.7.4