linux-kernel - [PATCH] sched/fair: calculate delta runnable load only when it's needed

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Message-Id: <20200103114400.17668-1-rocking@linux.alibaba.com>
Date:   Fri,  3 Jan 2020 19:44:00 +0800
From:   Peng Wang <rocking@...ux.alibaba.com>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de
Cc:     linux-kernel@...r.kernel.org, Peng Wang <rocking@...ux.alibaba.com>
Subject: [PATCH] sched/fair: calculate delta runnable load only when it's needed

Move the code of calculation for delta_sum/delta_avg to where
it is really needed to be done.

Signed-off-by: Peng Wang <rocking@...ux.alibaba.com>
---
 kernel/sched/fair.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ba749f579714..6b7e6b528e9b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3366,16 +3366,17 @@ update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cf
 
 	runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
 	runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);
-	delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum;
-	delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
-
-	se->avg.runnable_load_sum = runnable_sum;
-	se->avg.runnable_load_avg = runnable_load_avg;
 
 	if (se->on_rq) {
+		delta_sum = runnable_load_sum -
+				se_weight(se) * se->avg.runnable_load_sum;
+		delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
 		add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg);
 		add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum);
 	}
+
+	se->avg.runnable_load_sum = runnable_sum;
+	se->avg.runnable_load_avg = runnable_load_avg;
 }
 
 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
-- 
2.24.0