linux-kernel - Re: [PATCH 4/6 v8] sched/fair: Add push task mechanism for fair

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Message-ID: <CAKfTPtBC=m2EvKjQW8e+ad3yJdW5JeZWoH2Qhj0yygOJCyc3UA@mail.gmail.com>
Date: Thu, 4 Dec 2025 15:32:41 +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, pierre.gondois@....com, kprateek.nayak@....com, 
	qyousef@...alina.io, hongyan.xia2@....com, christian.loehle@....com, 
	luis.machado@....com
Subject: Re: [PATCH 4/6 v8] sched/fair: Add push task mechanism for fair

On Thu, 4 Dec 2025 at 11:46, Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Tue, Dec 02, 2025 at 07:12:40PM +0100, Vincent Guittot wrote:
>
>
> > +static void fair_add_pushable_task(struct rq *rq, struct task_struct *p)
> > +{
> > +     if (sched_push_task_enabled() && fair_push_task(rq, p)) {
> > +             plist_del(&p->pushable_tasks, &rq->cfs.pushable_tasks);
> > +             plist_node_init(&p->pushable_tasks, p->prio);
> > +             plist_add(&p->pushable_tasks, &rq->cfs.pushable_tasks);
> > +     }
> > +}
>
> I might have asked before, but if there was an answer, I have forgotten
> :/
>
> Why is this a prio-list? It seems to me that we don't particularly care
> about keeping this push sorted by nice value, right?

We re-use the same struct plist_node pushable_tasks field as rt in task_struct
and we might add some ordering later based on slice as an example

but other than that no other reason

>