linux-kernel - Re: [RFC][PATCH 1/3] cpuidle: Inject tick boundary state

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Message-ID: <20230729084417.GB3945851@hirez.programming.kicks-ass.net>
Date:   Sat, 29 Jul 2023 10:44:17 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     anna-maria@...utronix.de, tglx@...utronix.de, frederic@...nel.org,
        gautham.shenoy@....com, linux-kernel@...r.kernel.org,
        daniel.lezcano@...aro.org, linux-pm@...r.kernel.org,
        mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com
Subject: Re: [RFC][PATCH 1/3] cpuidle: Inject tick boundary state

On Fri, Jul 28, 2023 at 05:36:55PM +0200, Rafael J. Wysocki wrote:
> On Fri, Jul 28, 2023 at 5:01 PM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > In order to facilitate governors that track history in idle-state
> > buckets (TEO) making a useful decision about NOHZ, make sure we have a
> > bucket that counts tick-and-longer.
> >
> > In order to be inclusive of the tick itself -- after all, if we do not
> > disable NOHZ we'll sleep for a full tick, the actual boundary should
> > be just short of a full tick.
> >
> > IOW, when registering the idle-states, add one that is always
> > disabled, just to have a bucket.
> 
> This extra bucket can be created in the governor itself, can't it?

I couldn't find a nice spot for the governor to add idle-states.