linux-kernel - [PATCH 1/3] sched/fair: Fix statistics for find_idlest

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Date:   Tue,  3 Mar 2020 11:02:56 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Lukasz Luba <lukasz.luba@....com>,
        Phil Auld <pauld@...hat.com>, Hillf Danton <hdanton@...a.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        Paul McKenney <paulmck@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: [PATCH 1/3] sched/fair: Fix statistics for find_idlest_group()

From: Vincent Guittot <vincent.guittot@...aro.org>

From: Vincent Guittot <vincent.guittot@...aro.org>

sgs->group_weight is not set while gathering statistics in
update_sg_wakeup_stats(). This means that a group can be classified as
fully busy with 0 running tasks if utilization is high enough.

This path is mainly used for fork and exec.

Fixes: 57abff067a08 ("sched/fair: Rework find_idlest_group()")
Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Acked-by: Mel Gorman <mgorman@...hsingularity.net>
Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
Link: https://lore.kernel.org/r/20200218144534.4564-1-vincent.guittot@linaro.org
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fcc968669aea..4b5d5e5e701e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8561,6 +8561,8 @@ static inline void update_sg_wakeup_stats(struct sched_domain *sd,
 
 	sgs->group_capacity = group->sgc->capacity;
 
+	sgs->group_weight = group->group_weight;
+
 	sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
 
 	/*
-- 
2.16.4