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

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Date:   Fri, 15 Nov 2019 15:05:55 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux-kernel <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>,
        "open list:THERMAL" <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 02:37:27PM +0100, Vincent Guittot wrote:
> On Fri, 15 Nov 2019 at 14:25, Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > On Thu, Nov 14, 2019 at 06:07:31PM +0100, Vincent Guittot wrote:

> > > +     decayed = update_rt_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &rt_sched_class);
> > > +     decayed |= update_dl_rq_load_avg(rq_clock_pelt(rq), rq, curr_class == &dl_sched_class);
> > > +     decayed |= update_irq_load_avg(rq, 0);
> >
> > Should not all 3 have their windows aligned and thus alway return the
> > exact same value?
> 
> rt and dl yes but not irq

Any reason for IRQ not to be aligned?

> But having aligned window doesn't mean that they will all decay.
> One can have been updated just before (during a dequeue as an example)
> or at least less than 1ms before

Bah... true.