linux-kernel - Re: [PATCH 0/10 v2] sched/fair: Fix statistics with delayed dequeue

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Message-ID: <CAKfTPtDwS4+t0Fnacre6dtxKdxtrgua_2v=s7pZHqDsYoMMxFA@mail.gmail.com>
Date: Mon, 2 Dec 2024 10:17:53 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Mike Galbraith <efault@....de>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com, 
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, 
	mgorman@...e.de, vschneid@...hat.com, linux-kernel@...r.kernel.org, 
	kprateek.nayak@....com, pauld@...hat.com, luis.machado@....com
Subject: Re: [PATCH 0/10 v2] sched/fair: Fix statistics with delayed dequeue

On Sun, 1 Dec 2024 at 14:30, Mike Galbraith <efault@....de> wrote:
>
> Greetings,
>
> On Fri, 2024-11-29 at 17:17 +0100, Vincent Guittot wrote:
> > Delayed dequeued feature keeps a sleeping sched_entitiy enqueued until its
> > lag has elapsed. As a result, it stays also visible in the statistics that
> > are used to balance the system and in particular the field h_nr_running.
> >
> > This serie fixes those metrics by creating a new h_nr_queued that tracks
> > all queued tasks. It renames h_nr_running into h_nr_runnable and restores
> > the behavior of h_nr_running i.e. tracking the number of fair tasks that
> >  want to run.
> >
> > h_nr_runnable is used in several places to make decision on load balance:
> >   - PELT runnable_avg
> >   - deciding if a group is overloaded or has spare capacity
> >   - numa stats
> >   - reduced capacity management
> >   - load balance between groups
>
> I took the series for a spin in tip v6.12-10334-gb1b238fba309, but
> runnable seems to have an off-by-one issue, causing it to wander ever
> further south.
>
> patches 1-3 applied.
>   .h_nr_runnable                 : -3046
>   .runnable_avg                  : 450189777126

Yeah, I messed up something around finish_delayed_dequeue_entity().
I'm' going to prepare a v3

>
> full set applied.
>   .h_nr_runnable                 : -5707
>   .runnable_avg                  : 4391793519526
>
>         -Mike