From 9362cd8558353ed8de4648056992d9676ea9452d Mon Sep 17 00:00:00 2001
From: Peng Wang <rocking@linux.alibaba.com>
Date: Fri, 3 Jan 2020 19:44:00 +0800
Subject: [PATCH] sched/fair: calculate delta runnable load only when it's
 needed

References: bnc#1155798 (CPU scheduler functional and performance backports)
Patch-mainline: v5.6-rc1
Git-commit: fe71bbb21ee14160f73f81b113d71145327a1c0d

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@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20200103114400.17668-1-rocking@linux.alibaba.com
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 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 cb953a08bbef..b74cc4402bc3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3367,16 +3367,17 @@ 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)