linux-kernel - Re: [PATCH] sched/idle: Make idle poll dynamic per-cpu

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Message-ID: <Y8U69WeQgvgjQdhj@hirez.programming.kicks-ass.net>
Date:   Mon, 16 Jan 2023 12:54:29 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Daniel Bristot de Oliveira <bristot@...nel.org>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Joe Mario <jmario@...hat.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH] sched/idle: Make idle poll dynamic per-cpu

On Mon, Jan 16, 2023 at 10:28:20AM +0100, Ingo Molnar wrote:
> 
> * Ingo Molnar <mingo@...nel.org> wrote:
> 
> > > Urgh, can we please make this a cpuidle governor thing or so? So that 
> > > we don't need to invent new interfaces and such.
> > 
> > I think the desired property here would be to make this interface on top 
> > of pretty much any governor. Ie. have a governor, but also a way to drop 
> > any CPU into idle-poll, overriding that.
> 
> ... with the goal of having the best governor for power efficiency by 
> default - but also the ability to drop a handful of CPUs into the highest 
> performance / lowest latency idle mode.

Bah, so while you can set a cpufreq gov (say performance) per cpu,
you can't do the same with cpuidle.