linux-kernel - Re: [PATCH 7/9] sched/fair: Do not try to migrate delayed dequeue task

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Message-ID: <20241128101549.GD24400@noisy.programming.kicks-ass.net>
Date: Thu, 28 Nov 2024 11:15:49 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Vincent Guittot <vincent.guittot@...aro.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 7/9] sched/fair: Do not try to migrate delayed dequeue
 task

On Thu, Nov 28, 2024 at 11:03:44AM +0100, Vincent Guittot wrote:
> On Thu, 28 Nov 2024 at 10:49, Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > On Thu, Nov 28, 2024 at 10:27:48AM +0100, Vincent Guittot wrote:
> > > Migrating a delayed dequeued task doesn't help in balancing the number
> > > of runnable tasks in the system.
> >
> > But it can help balance the weight; furthermore, by moving them to a
> > lighter queue, they'll get picked sooner and disappear sooner.
> 
> When groups are not overloaded, we don't compare load but only running
> tasks t balance them across cpus
> 
> It's only when both src and dst groups are overloaded that we look at
> the load and the weight
> 
> >
> > Perhaps make it: p->se.sched_delayed && !env->sd->nr_balance_failed ?
> 
> So we could take into account which type of migration with
> env->migration_type == migrate_load

Yeah that makes sense.