linux-kernel - Re: [PATCH 4/4] sched/fair: Revert 6d71a9c61604 ("sched/fair: Fix EEVDF entity placement bug causing scheduling lag")

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Message-ID: <20260131152135.GA509491@noisy.programming.kicks-ass.net>
Date: Sat, 31 Jan 2026 16:21:35 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Zhang Qiao <zhangqiao22@...wei.com>
Cc: mingo@...nel.org, juri.lelli@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, linux-kernel@...r.kernel.org,
	wangtao554@...wei.com, quzicheng@...wei.com, kprateek.nayak@....com,
	wuyun.abel@...edance.com, dsmythies@...us.net,
	Hui Tang <tanghui20@...wei.com>
Subject: Re: [PATCH 4/4] sched/fair: Revert 6d71a9c61604 ("sched/fair: Fix
 EEVDF entity placement bug causing scheduling lag")

On Sat, Jan 31, 2026 at 09:47:07AM +0800, Zhang Qiao wrote:

> >  	if (se->on_rq) {
> >  		/* commit outstanding execution time */
> >  		update_curr(cfs_rq);
> > -		update_entity_lag(cfs_rq, se);
> > -		se->deadline -= se->vruntime;
> > +		avruntime = avg_vruntime(cfs_rq);
> > +		se->vlag = entity_lag(avruntime, se);
> 
> 
> vlag is updated here. Considering vlag and vprot share the same union, updating
> vlag will overwrite vprot. Is it right to call protect_slice() (which use vprot)
> after this update?

Oh you are quite right; I'm sure Ingo had a patch removing that union,
but clearly that's not been merged yet.

Sorry about that mistake; I'll make a new version on Monday.

Thanks!