Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable

From	Steve Muckle <steve.muckle@linaro.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable
Date	2016-03-16 04:40 +0100
Message-ID	<rdatt-3a4-39@gated-at.bofh.it> (permalink)
References	(1 earlier) <rcteN-7Q2-9@gated-at.bofh.it> <rd4Hn-7Mu-1@gated-at.bofh.it> <rd50L-7UJ-37@gated-at.bofh.it> <rd50L-7UJ-35@gated-at.bofh.it> <rdatt-3a4-41@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 03/15/2016 03:37 PM, Michael Turquette wrote:
>>>> Yuck sysfs.. I would really rather we did not expose this per default.
>>>> > > > And certainly not in this weird form.
>>> > > 
>>> > > I'm happy to change capacity_margin to up_threshold and use a
>>> > > percentage.
>>> > > 
>>> > > The sysfs approach has two benefits. First, it is aligned with cpufreq
>>> > > user expectations. Second, there has been rough consensus that this
>>> > > value should be tunable and sysfs gets us there quickly and painlessly.
>>> > > We're already exporting rate_limit_us for schedutil via sysfs. Is there
>>> > > a better way interface you can recommend?
>> > 
>> > It really depends on how tunable you want this to be. Do we always want
>> > this to be a tunable, or just now while we're playing about with the
>> > whole thing?
>
> I had considered this myself, and I really think that Steve and Juri
> should chime in as they have spent more time tuning and running the
> numbers.
> 
> I'm inclined to think that a debug version would be good enough, as I
> don't imagine this value being changed at run-time by some userspace
> daemon or something.
> 
> Then again, maybe this knob will be part of the mythical
> power-vs-performance slider?

Patrick Bellasi's schedtune series [0] (which I think is the referenced
mythical slider) aims to provide a more sophisticated interface for
tuning scheduler-driven frequency selection. In addition to a global
boost value it includes a cgroup controller as well for per-task tuning.

I would definitely expect the margin/boost value to be modified at
runtime, for example if the battery is running low, or the user wants
100% performance for a while, or the userspace framework wants to
temporarily tailor the performance level for a particular set of tasks, etc.

[0] http://article.gmane.org/gmane.linux.kernel/2022959

Thread

[PATCH 0/8] schedutil enhancements Michael Turquette <mturquette@baylibre.com> - 2016-03-14 06:30 +0100
  [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Michael Turquette <mturquette@baylibre.com> - 2016-03-14 06:30 +0100
    Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Peter Zijlstra <peterz@infradead.org> - 2016-03-15 22:30 +0100
      Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Peter Zijlstra <peterz@infradead.org> - 2016-03-15 22:50 +0100
        Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Steve Muckle <steve.muckle@linaro.org> - 2016-03-16 04:40 +0100
          Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Peter Zijlstra <peterz@infradead.org> - 2016-03-16 09:10 +0100
            Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Juri Lelli <Juri.Lelli@arm.com> - 2016-03-16 11:10 +0100
              Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Steve Muckle <steve.muckle@linaro.org> - 2016-03-16 19:00 +0100
                Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Michael Turquette <mturquette@baylibre.com> - 2016-03-16 23:10 +0100
                Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Juri Lelli <Juri.Lelli@arm.com> - 2016-03-17 10:40 +0100
                Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Steve Muckle <steve.muckle@linaro.org> - 2016-03-17 15:00 +0100
                Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Patrick Bellasi <patrick.bellasi@arm.com> - 2016-03-17 17:00 +0100
            Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable "Rafael J. Wysocki" <rafael@kernel.org> - 2016-03-16 13:50 +0100
          Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Michael Turquette <mturquette@baylibre.com> - 2016-03-16 23:10 +0100
  [PATCH 1/8] sched/cpufreq: remove cpufreq_trigger_update() Michael Turquette <mturquette@baylibre.com> - 2016-03-14 06:30 +0100
    Re: [PATCH 1/8] sched/cpufreq: remove cpufreq_trigger_update() Peter Zijlstra <peterz@infradead.org> - 2016-03-15 22:20 +0100
      Re: [PATCH 1/8] sched/cpufreq: remove cpufreq_trigger_update() Peter Zijlstra <peterz@infradead.org> - 2016-03-15 23:00 +0100
    Re: [PATCH 1/8] sched/cpufreq: remove cpufreq_trigger_update() Peter Zijlstra <peterz@infradead.org> - 2016-03-16 09:10 +0100
  [PATCH 5/8] sched/cpufreq: pass sched class into cpufreq_update_util Michael Turquette <mturquette@baylibre.com> - 2016-03-14 06:30 +0100
    Re: [PATCH 5/8] sched/cpufreq: pass sched class into  cpufreq_update_util Peter Zijlstra <peterz@infradead.org> - 2016-03-15 22:30 +0100
      Re: [PATCH 5/8] sched/cpufreq: pass sched class into  cpufreq_update_util Steve Muckle <steve.muckle@linaro.org> - 2016-03-16 05:00 +0100
      Re: [PATCH 5/8] sched/cpufreq: pass sched class into  cpufreq_update_util Peter Zijlstra <peterz@infradead.org> - 2016-03-16 08:50 +0100
        Re: [PATCH 5/8] sched/cpufreq: pass sched class into cpufreq_update_util Vincent Guittot <vincent.guittot@linaro.org> - 2016-03-16 09:40 +0100
          Re: [PATCH 5/8] sched/cpufreq: pass sched class into  cpufreq_update_util Peter Zijlstra <peterz@infradead.org> - 2016-03-16 10:00 +0100
            Re: [PATCH 5/8] sched/cpufreq: pass sched class into cpufreq_update_util Vincent Guittot <vincent.guittot@linaro.org> - 2016-03-16 10:20 +0100
            Re: [PATCH 5/8] sched/cpufreq: pass sched class into cpufreq_update_util "Rafael J. Wysocki" <rafael@kernel.org> - 2016-03-16 13:40 +0100
              Re: [PATCH 5/8] sched/cpufreq: pass sched class into  cpufreq_update_util Peter Zijlstra <peterz@infradead.org> - 2016-03-16 14:20 +0100
                Re: [PATCH 5/8] sched/cpufreq: pass sched class into cpufreq_update_util "Rafael J. Wysocki" <rafael@kernel.org> - 2016-03-16 14:30 +0100
                Re: [PATCH 5/8] sched/cpufreq: pass sched class into  cpufreq_update_util Peter Zijlstra <peterz@infradead.org> - 2016-03-16 14:50 +0100
  [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Michael Turquette <mturquette@baylibre.com> - 2016-03-14 06:30 +0100
    Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Dietmar Eggemann <dietmar.eggemann@arm.com> - 2016-03-15 20:20 +0100
      Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Michael Turquette <mturquette@baylibre.com> - 2016-03-15 21:50 +0100
        Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Dietmar Eggemann <dietmar.eggemann@arm.com> - 2016-03-16 20:50 +0100
          Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Peter Zijlstra <peterz@infradead.org> - 2016-03-16 21:10 +0100
            Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-03-16 22:40 +0100
    Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Peter Zijlstra <peterz@infradead.org> - 2016-03-15 22:50 +0100
      Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Peter Zijlstra <peterz@infradead.org> - 2016-03-16 08:50 +0100
        Re: [PATCH 8/8] sched: prefer cpufreq_scale_freq_capacity Peter Zijlstra <peterz@infradead.org> - 2016-03-16 13:50 +0100
  [PATCH 2/8] sched/fair: add margin to utilization update Michael Turquette <mturquette@baylibre.com> - 2016-03-14 06:30 +0100
    Re: [PATCH 2/8] sched/fair: add margin to utilization update Peter Zijlstra <peterz@infradead.org> - 2016-03-15 22:20 +0100
      Re: [PATCH 2/8] sched/fair: add margin to utilization update Peter Zijlstra <peterz@infradead.org> - 2016-03-15 22:50 +0100
    Re: [PATCH 2/8] sched/fair: add margin to utilization update Steve Muckle <steve.muckle@linaro.org> - 2016-03-16 04:00 +0100
      Re: [PATCH 2/8] sched/fair: add margin to utilization update Michael Turquette <mturquette@baylibre.com> - 2016-03-16 23:20 +0100
  [PATCH 3/8] sched/cpufreq: new cfs capacity margin helpers Michael Turquette <mturquette@baylibre.com> - 2016-03-14 06:30 +0100
    Re: [PATCH 3/8] sched/cpufreq: new cfs capacity margin helpers Peter Zijlstra <peterz@infradead.org> - 2016-03-15 22:20 +0100
  Re: [PATCH 0/8] schedutil enhancements "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-03-16 01:10 +0100

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