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

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Date:   Tue, 3 Mar 2020 12:14:07 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.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>
Subject: Re: [PATCH 1/3] sched/fair: Fix statistics for find_idlest_group()

Hi Mel,

On Tue, 3 Mar 2020 at 12:03, Mel Gorman <mgorman@...hsingularity.net> wrote:
>
> 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

This one has been merged in tip/sched/urgent

> ---
>  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
>