linux-kernel - Re: [PATCH 2/2] sched/fair: Reimplement NEXT

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Message-ID: <20251103141421.GW4068168@noisy.programming.kicks-ass.net>
Date: Mon, 3 Nov 2025 15:14:21 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Mel Gorman <mgorman@...hsingularity.net>
Cc: Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Valentin Schneider <vschneid@...hat.com>,
	Chris Mason <clm@...a.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] sched/fair: Reimplement NEXT_BUDDY to align with
 EEVDF goals

On Mon, Nov 03, 2025 at 03:07:11PM +0100, Peter Zijlstra wrote:

> > @@ -8734,7 +8819,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
> >  	struct sched_entity *se = &donor->se, *pse = &p->se;
> >  	struct cfs_rq *cfs_rq = task_cfs_rq(donor);
> >  	int cse_is_idle, pse_is_idle;
> > -	bool do_preempt_short = false;
> > +	enum preempt_wakeup_action preempt_action = PREEMPT_WAKEUP_NONE;
> 
> I'm thinking NONE is the wrong default

That was unfinished, kid interrupted me at an inopportune moment and I
lost my train ;-)

Anyway, the current code defaults to what will be 'pick'. And I suppose
we could make the default depend on WAKEUP_PREEMPT but meh.