linux-kernel - [PATCH 5.5 180/189] sched/fair: Fix statistics for find_idlest

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Date:   Tue, 10 Mar 2020 13:40:17 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: [PATCH 5.5 180/189] sched/fair: Fix statistics for find_idlest_group()

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

commit 289de35984815576793f579ec27248609e75976e upstream.

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>
Link: https://lore.kernel.org/r/20200218144534.4564-1-vincent.guittot@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8315,6 +8315,8 @@ static inline void update_sg_wakeup_stat
 
 	sgs->group_capacity = group->sgc->capacity;
 
+	sgs->group_weight = group->group_weight;
+
 	sgs->group_type = group_classify(sd->imbalance_pct, group, sgs);
 
 	/*