linux-kernel - [PATCH 0/2] schd/fair: fix stalled cfs_rq->tg_load_avg

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Message-Id: <20210527122916.27683-1-vincent.guittot@linaro.org>
Date:   Thu, 27 May 2021 14:29:14 +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 0/2] schd/fair: fix stalled cfs_rq->tg_load_avg_contrib

Odin reported some fairness problem between cgroup because of stalled
value in cfs_rq->tg_load_avg_contrib:

https://lkml.org/lkml/2021/5/18/566


2 problems generated this situation:
-1st: After propagating load in the hierarchy, load_sum can be null
 whereas load_avg isn't so the cfs_rq is removed whereas it still
 contribute to th tg's load
-2nd: cfs_rq->tg_load_avg_contrib was not always updated after
 significant changes like becoming null because cfs_rq had already
 been updated when propagating a child load.


Vincent Guittot (2):
  sched/fair: keep load_avg and load_sum synced
  sched/fair: make sure to update tg contrib for blocked load

 kernel/sched/fair.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

-- 
2.17.1