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

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Message-ID: <227863d758551e75cd0807a5f1f31916d695205b.camel@gmx.de>
Date: Sun, 01 Dec 2024 14:30:05 +0100
From: Mike Galbraith <efault@....de>
To: Vincent Guittot <vincent.guittot@...aro.org>, 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
Cc: kprateek.nayak@....com, pauld@...hat.com, luis.machado@....com
Subject: Re: [PATCH 0/10 v2] sched/fair: Fix statistics with delayed dequeue

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

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

	-Mike