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

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Message-ID: <CAKfTPtAmidDzBRE7UGqodaVfyge1M9D0Q8M_EX2ojqYW2Y8V=A@mail.gmail.com>
Date: Mon, 2 Dec 2024 10:59:42 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Luis Machado <luis.machado@....com>
Cc: Mike Galbraith <efault@....de>, 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
Subject: Re: [PATCH 0/10 v2] sched/fair: Fix statistics with delayed dequeue

On Mon, 2 Dec 2024 at 10:23, Luis Machado <luis.machado@....com> wrote:
>
> On 12/2/24 09:17, Vincent Guittot wrote:
> > 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>
>
> Maybe something similar to what I ran into here?
>
> https://lore.kernel.org/lkml/6df12fde-1e0d-445f-8f8a-736d11f9ee41@arm.com/

I'm going to have a look

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