linux-kernel - [PATCH 1/2] sched/fair: keep load_avg and load

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Message-Id: <20210527122916.27683-2-vincent.guittot@linaro.org>
Date:   Thu, 27 May 2021 14:29:15 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, linux-kernel@...r.kernel.org,
        odin@...d.al, cgroups@...r.kernel.org
Cc:     Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 1/2] sched/fair: keep load_avg and load_sum synced

when removing a cfs_rq from the list we only check _sum value so we must
ensure that _avg and _sum stay synced so load_sum can't be null whereas
load_avg is not after propagating load in the cgroup hierarchy.

Use load_avg to compute load_sum similarly to what is done for util_sum
and runnable_sum.

Fixes: 0e2d2aaaae52 ("sched/fair: Rewrite PELT migration propagation")
Reported-by: Odin Ugedal <odin@...d.al>
Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
---
 kernel/sched/fair.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 161b92aa1c79..2859545d95fb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3509,7 +3509,8 @@ update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq
 	se->avg.load_sum = runnable_sum;
 	se->avg.load_avg = load_avg;
 	add_positive(&cfs_rq->avg.load_avg, delta_avg);
-	add_positive(&cfs_rq->avg.load_sum, delta_sum);
+	cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * divider;
+
 }
 
 static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
-- 
2.17.1