linux-kernel - Re: [PATCH 03/10 v2] sched/fair: Add new cfs_rq.h_nr

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Message-ID: <CAKfTPtAJh=e0dci7sKNOBuyEoYY5v0TqFoa4YeJ1X7VTzTeT4Q@mail.gmail.com>
Date: Mon, 2 Dec 2024 10:57:59 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: mingo@...hat.com, 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, 
	efault@....de, luis.machado@....com
Subject: Re: [PATCH 03/10 v2] sched/fair: Add new cfs_rq.h_nr_runnable

On Mon, 2 Dec 2024 at 10:54, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Fri, Nov 29, 2024 at 05:17:49PM +0100, Vincent Guittot wrote:
> > With delayed dequeued feature, a sleeping sched_entity remains queued in
> > the rq 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 cfs.h_nr_queued when the sched_entity is associated to a task.
> >
> > Create a new h_nr_runnable that tracks all queued and runnable tasks and
> > use it when balancing the load on the system.
> >
> > h_nr_runnable will be 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
> > - nohz kick
> >
> > It should be noticed that the rq->nr_running still counts the delayed
> > dequeued tasks as delayed dequeue is a fair feature that is meaningless
> > at core level.
>
> Since you're doing a v3, could you please split this into 2 patches, one
> adding the accounting, and then a separate patch making use of it?

ok