linux-kernel - Re: [PATCH 11/15] sched/eevdf: Better handle mixed slice length

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Date:   Sat, 10 Jun 2023 13:22:41 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     mingo@...nel.org, vincent.guittot@...aro.org,
        linux-kernel@...r.kernel.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, corbet@....net,
        qyousef@...alina.io, chris.hyser@...cle.com,
        patrick.bellasi@...bug.net, pjt@...gle.com, pavel@....cz,
        qperret@...gle.com, tim.c.chen@...ux.intel.com, joshdon@...gle.com,
        timj@....org, kprateek.nayak@....com, youssefesmat@...omium.org,
        joel@...lfernandes.org, efault@....de, tglx@...utronix.de
Subject: Re: [PATCH 11/15] sched/eevdf: Better handle mixed slice length

On Sat, Jun 10, 2023 at 02:34:04PM +0800, Chen Yu wrote:

> > +static inline bool
> > +entity_has_slept(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> > +{
> > +	u64 now;
> > +
> > +	if (!(flags & ENQUEUE_WAKEUP))
> > +		return false;
> > +
> > +	if (flags & ENQUEUE_MIGRATED)
> > +		return true;
> > +
> > +	now = rq_clock_task(rq_of(cfs_rq));
> > +	return (s64)(se->exec_start - now) >= se->slice;
> > +}
> A minor question, should it be now - se->exec_start ?
> (se->exec_start - now) is always negetive on local wakeup?

Yeah, also:

https://lkml.kernel.org/r/20230608124440.GB1002251@hirez.programming.kicks-ass.net

That is, it should be something along the lines of:

	delta = new - se->exec->start
	rerturn delta/W > vslice