Re: [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits
Date	2016-11-21 16:40 +0100
Message-ID	<sFYRk-2Wx-31@gated-at.bofh.it> (permalink)
References	(3 earlier) <sFVJL-15x-9@gated-at.bofh.it> <sFVTr-18L-9@gated-at.bofh.it> <sFXiC-1QC-13@gated-at.bofh.it> <sFYeC-2u5-27@gated-at.bofh.it> <sFYHJ-2Tm-31@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Mon, Nov 21, 2016 at 04:26:06PM +0100, Peter Zijlstra wrote:
> > For example, a task running 30 [ms] every 100 [ms] is a ~300 util_avg
> > task. With PELT, we get a signal which range between [120,550] with an
> > average of ~300 which is instead completely ignored. By capping the
> > decay we will get:
> > 
> >    decay_cap [ms]      range    average
> >                 0      120:550     300
> >                64      140:560     310
> >                32      320:660     430
> > 
> > which means that still the raw PELT signal is wobbling and never
> > provides a consistent response to drive decisions.
> > 
> > Thus, a "predictor" should be something which sample information from
> > PELT to provide a more consistent view, a sort of of low-pass filter
> > on top of the "dynamic metric" which is PELT.

Note that a simple low-pass IIR filter will only shrink the wobble, not
take it out entirely. Or rather, if you make it so strong as to take the
entire wobble out, it'll likely react like molasses.

Thread

[PATCH] cpufreq: schedutil: add up/down frequency transition rate limits Viresh Kumar <viresh.kumar@linaro.org> - 2016-11-17 06:30 +0100
  Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Viresh Kumar <viresh.kumar@linaro.org> - 2016-11-21 11:10 +0100
    Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Peter Zijlstra <peterz@infradead.org> - 2016-11-21 11:20 +0100
      Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Viresh Kumar <viresh.kumar@linaro.org> - 2016-11-21 11:50 +0100
        Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Peter Zijlstra <peterz@infradead.org> - 2016-11-21 12:20 +0100
          Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Viresh Kumar <viresh.kumar@linaro.org> - 2016-11-21 12:40 +0100
            Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Peter Zijlstra <peterz@infradead.org> - 2016-11-21 12:50 +0100
      Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Juri Lelli <Juri.Lelli@arm.com> - 2016-11-21 13:20 +0100
        Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Peter Zijlstra <peterz@infradead.org> - 2016-11-21 13:30 +0100
          Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Juri Lelli <Juri.Lelli@arm.com> - 2016-11-21 15:00 +0100
            Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Peter Zijlstra <peterz@infradead.org> - 2016-11-21 15:20 +0100
              Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Juri Lelli <Juri.Lelli@arm.com> - 2016-11-21 15:40 +0100
                Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Peter Zijlstra <peterz@infradead.org> - 2016-11-21 15:50 +0100
                Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Juri Lelli <Juri.Lelli@arm.com> - 2016-11-21 16:00 +0100
                Re: [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits Vincent Guittot <vincent.guittot@linaro.org> - 2016-11-22 10:30 +0100
                Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Patrick Bellasi <patrick.bellasi@arm.com> - 2016-11-22 12:10 +0100
            Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Patrick Bellasi <patrick.bellasi@arm.com> - 2016-11-21 16:00 +0100
              Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Peter Zijlstra <peterz@infradead.org> - 2016-11-21 16:30 +0100
                Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Peter Zijlstra <peterz@infradead.org> - 2016-11-21 16:40 +0100
                Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Patrick Bellasi <patrick.bellasi@arm.com> - 2016-11-21 17:30 +0100
                Re: [PATCH] cpufreq: schedutil: add up/down frequency transition  rate limits Peter Zijlstra <peterz@infradead.org> - 2016-11-21 17:50 +0100
                Re: [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits "Rafael J. Wysocki" <rafael@kernel.org> - 2016-11-21 22:00 +0100

csiph-web