linux-kernel - Re: [PATCH v4] sched/freq: move call to cpufreq_update

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Date:   Fri, 15 Nov 2019 11:40:52 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mel Gorman <mgorman@...e.de>,
        Doug Smythies <dsmythies@...us.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sargun Dhillon <sargun@...gun.me>, Tejun Heo <tj@...nel.org>,
        Xie XiuQi <xiexiuqi@...wei.com>, xiezhipeng1@...wei.com,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH v4] sched/freq: move call to cpufreq_update_util

On Fri, Nov 15, 2019 at 11:03:20AM +0100, Rafael J. Wysocki wrote:
> On Fri, Nov 15, 2019 at 10:55 AM Peter Zijlstra <peterz@...radead.org> wrote:

> > So why are we making the scheduler code more ugly instead of fixing that
> > driver?
> 
> I guess we could "fix" the driver by making it rate limit MSR writes
> only, but I'm not sure if that would help.

So it is not clear to me what exactly intel_pstate needs and why. Like I
wrote in my reply to Vincent just now, it can still store the last
value, even if it doesn't act on it right away.

And it can then act on that stored value at a later event, whatever is
appropriate.

I'm just saying that generating superfluous events is silly. But
possibly I read the patch wrong.