linux-kernel - Re: [PATCH] sched/fair: fix runnable

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Date:   Wed, 26 Feb 2020 22:01:36 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Ben Segall <bsegall@...gle.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mel Gorman <mgorman@...e.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Phil Auld <pauld@...hat.com>, Parth Shah <parth@...ux.ibm.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Hillf Danton <hdanton@...a.com>, zhout@...aldi.net
Subject: Re: [PATCH] sched/fair: fix runnable_avg for throttled cfs

On Wed, 26 Feb 2020 at 20:04, <bsegall@...gle.com> wrote:
>
> Vincent Guittot <vincent.guittot@...aro.org> writes:
>
> > When a cfs_rq is throttled, its group entity is dequeued and its running
> > tasks are removed. We must update runnable_avg with current h_nr_running
> > and update group_se->runnable_weight with new h_nr_running at each level
> > of the hierarchy.
>
> You'll also need to do this for task enqueue/dequeue inside of a
> throttled hierarchy, I'm pretty sure.

AFAICT, this is already done with patch "sched/pelt: Add a new
runnable average signal" when task is enqueued/dequeued inside a
throttled hierarchy

>
> >
> > Fixes: 9f68395333ad ("sched/pelt: Add a new runnable average signal")
> > Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> > ---
> > This patch applies on top of tip/sched/core
> >
> >  kernel/sched/fair.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index fcc968669aea..6d46974e9be7 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -4703,6 +4703,11 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
> >
> >               if (dequeue)
> >                       dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
> > +             else {
> > +                     update_load_avg(qcfs_rq, se, 0);
> > +                     se_update_runnable(se);
> > +             }
> > +
> >               qcfs_rq->h_nr_running -= task_delta;
> >               qcfs_rq->idle_h_nr_running -= idle_task_delta;
> >
> > @@ -4772,6 +4777,11 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
> >               cfs_rq = cfs_rq_of(se);
> >               if (enqueue)
> >                       enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
> > +             else {
> > +                     update_load_avg(cfs_rq, se, 0);
>
>
> > +                     se_update_runnable(se);
> > +             }
> > +
> >               cfs_rq->h_nr_running += task_delta;
> >               cfs_rq->idle_h_nr_running += idle_task_delta;