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Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks

From "Rafael J. Wysocki" <rafael@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks
Date 2016-02-12 17:10 +0100
Message-ID <r1osa-Pl-25@gated-at.bofh.it> (permalink)
References (5 earlier) <r0Yep-8w1-67@gated-at.bofh.it> <r12UG-3l3-13@gated-at.bofh.it> <r13nH-3uV-3@gated-at.bofh.it> <r14D9-4iJ-25@gated-at.bofh.it> <r1mJI-87O-9@gated-at.bofh.it>
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On Fri, Feb 12, 2016 at 3:10 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Thu, Feb 11, 2016 at 10:52:20AM -0800, Steve Muckle wrote:
>> On 02/11/2016 09:30 AM, Peter Zijlstra wrote:
>> >> My concern above is that pokes are guaranteed to keep occurring when
>> >> > there is only RT or DL activity so nothing breaks.
>> >
>> > The hook in their respective tick handler should ensure stuff is called
>> > sporadically and isn't stalled.
>>
>> But that's only true if the RT/DL tasks happen to be running when the
>> tick arrives right?
>>
>> Couldn't we have RT/DL activity which doesn't overlap with the tick? And
>> if no CFS tasks happen to be executing on that CPU, we'll never trigger
>> the cpufreq update. This could go on for an arbitrarily long time
>> depending on the periodicity of the work.
>
> Possible yes, but why do we care? Such a CPU would be so much idle that
> cpufreq doesn't matter one way or another, right?

Well, in theory you can get 50% or so of the time active in bursts
that happen to fit between ticks.  If we happen to do those in the
lowest P-state, we may burn more energy than necessary on platforms
where more idle is preferred.

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Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-02-09 21:10 +0100
  Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Steve Muckle <steve.muckle@linaro.org> - 2016-02-10 02:10 +0100
    Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-10 03:00 +0100
      Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-10 04:10 +0100
        Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Steve Muckle <steve.muckle@linaro.org> - 2016-02-10 20:50 +0100
          Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-10 22:50 +0100
            Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Steve Muckle <steve.muckle@linaro.org> - 2016-02-10 23:10 +0100
              Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-10 23:20 +0100
    Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Peter Zijlstra <peterz@infradead.org> - 2016-02-11 13:10 +0100
      Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Juri Lelli <juri.lelli@arm.com> - 2016-02-11 13:30 +0100
        Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Peter Zijlstra <peterz@infradead.org> - 2016-02-11 16:30 +0100
          Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks Vincent Guittot <vincent.guittot@linaro.org> - 2016-02-11 19:30 +0100
            Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Peter Zijlstra <peterz@infradead.org> - 2016-02-12 15:10 +0100
              Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks Vincent Guittot <vincent.guittot@linaro.org> - 2016-02-12 15:50 +0100
      Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Steve Muckle <steve.muckle@linaro.org> - 2016-02-11 18:10 +0100
        Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-11 18:40 +0100
          Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Peter Zijlstra <peterz@infradead.org> - 2016-02-11 18:40 +0100
        Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Peter Zijlstra <peterz@infradead.org> - 2016-02-11 18:40 +0100
          Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Steve Muckle <steve.muckle@linaro.org> - 2016-02-11 20:00 +0100
            Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-11 20:10 +0100
              Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-12 14:50 +0100
            Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Peter Zijlstra <peterz@infradead.org> - 2016-02-12 15:20 +0100
              Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-12 17:10 +0100
                Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-12 17:20 +0100
                Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks Ashwin Chaugule <ashwin.chaugule@linaro.org> - 2016-02-12 18:00 +0100
                Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-13 00:20 +0100
                RE: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Doug Smythies" <dsmythies@telus.net> - 2016-02-12 18:10 +0100
                Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-13 00:20 +0100
  Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Juri Lelli <juri.lelli@arm.com> - 2016-02-10 13:40 +0100
    Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-10 14:30 +0100
      Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Juri Lelli <juri.lelli@arm.com> - 2016-02-10 15:10 +0100
        Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-10 15:30 +0100
          Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Juri Lelli <juri.lelli@arm.com> - 2016-02-10 15:50 +0100
            Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-10 16:50 +0100
              Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Juri Lelli <juri.lelli@arm.com> - 2016-02-10 17:10 +0100
  Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Peter Zijlstra <peterz@infradead.org> - 2016-02-11 13:00 +0100
    Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-11 13:10 +0100
      Re: [PATCH 0/3] cpufreq: Replace timers with utilization update  callbacks Peter Zijlstra <peterz@infradead.org> - 2016-02-11 16:30 +0100
        Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-11 17:00 +0100
      Re: [PATCH 0/3] cpufreq: Replace timers with utilization update callbacks "Rafael J. Wysocki" <rafael@kernel.org> - 2016-02-11 21:50 +0100

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