Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support
Date	2017-07-13 16:50 +0200
Message-ID	<u2NBf-6SY-7@gated-at.bofh.it> (permalink)
References	(5 earlier) <u2h8m-39O-23@gated-at.bofh.it> <u2llE-5Pi-17@gated-at.bofh.it> <u2m81-6pg-11@gated-at.bofh.it> <u2nQt-7wc-9@gated-at.bofh.it> <u2MYy-6BL-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Jul 13, 2017 at 03:04:09PM +0100, Sudeep Holla wrote:

> The question is whether we *need* to know the completion of frequency
> transition. What is the impact of absence of it ? I am considering
> platforms which may take up to a ms or more to do the actual transition
> in the firmware.

So on x86 we can recover from not knowing by means of the APERF/MPERF
thing, which gives us the average effective frequency over the last
period.

If you lack that you need something to update the actual effective
frequency.

Changing the effective frequency at request time might confuse things --
esp. if the request might not be honoured at all or can take a
significant time to complete. Not to mention that _IF_ you rely on the
effective frequency to set other clocks things can come unstuck.

So unless you go the whole distance and do APERF/MPERF like things, I
think it would be very good to have a notification of completion (and
possibly a read-back of the effective frequency that is now set).

Thread

[PATCH v2 00/10] arm, arm64: frequency- and cpu-invariant accounting support for task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
  [PATCH v2 08/10] arm64: wire frequency-invariant accounting support up to the task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
    Re: [PATCH v2 08/10] arm64: wire frequency-invariant accounting  support up to the task scheduler Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
  [PATCH v2 03/10] drivers base/arch_topology: frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
    Re: [PATCH v2 03/10] drivers base/arch_topology: frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
      Re: [PATCH v2 03/10] drivers base/arch_topology: frequency-invariant  load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-07 19:00 +0200
  [PATCH v2 05/10] arm: wire frequency-invariant accounting support up to the task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
    Re: [PATCH v2 05/10] arm: wire frequency-invariant accounting  support up to the task scheduler Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
  [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
    Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
      Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-07 00:50 +0200
      Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-07 18:10 +0200
        Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support "Rafael J. Wysocki" <rafael@kernel.org> - 2017-07-07 18:20 +0200
          Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-07 19:10 +0200
            Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-08 14:20 +0200
              Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-10 09:00 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-10 15:00 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-11 08:50 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-11 17:30 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 14:50 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-13 15:10 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 16:10 +0200
              Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-10 11:40 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-10 11:50 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-10 12:40 +0200
              Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-10 14:10 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-11 08:10 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-11 17:10 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-11 17:10 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-11 17:20 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-12 06:10 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-12 10:40 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-12 11:30 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-12 13:20 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant load-tracking support "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-07-13 01:30 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-13 10:00 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-13 10:50 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-13 13:20 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 16:10 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Peter Zijlstra <peterz@infradead.org> - 2017-07-13 16:50 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 17:10 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 15:00 +0200
                Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Sudeep Holla <sudeep.holla@arm.com> - 2017-07-13 14:50 +0200
        Re: [PATCH v2 02/10] cpufreq: provide data for frequency-invariant  load-tracking support Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-10 08:50 +0200
  [PATCH v2 04/10] arm: wire cpufreq input data for frequency-invariant accounting up to the arch Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
    Re: [PATCH v2 04/10] arm: wire cpufreq input data for  frequency-invariant accounting up to the arch Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
      Re: [PATCH v2 04/10] arm: wire cpufreq input data for  frequency-invariant accounting up to the arch Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-10 17:20 +0200
        Re: [PATCH v2 04/10] arm: wire cpufreq input data for  frequency-invariant accounting up to the arch Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-11 08:40 +0200
  [PATCH v2 09/10] arm64: wire cpu-invariant accounting support up to the task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
    Re: [PATCH v2 09/10] arm64: wire cpu-invariant accounting support up  to the task scheduler Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
  [PATCH v2 06/10] arm: wire cpu-invariant accounting support up to the task scheduler Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
    Re: [PATCH v2 06/10] arm: wire cpu-invariant accounting support up  to the task scheduler Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:50 +0200
  [PATCH v2 01/10] drivers base/arch_topology: free cpumask cpus_to_visit Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
    Re: [PATCH v2 01/10] drivers base/arch_topology: free cpumask  cpus_to_visit Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 12:30 +0200
      Re: [PATCH v2 01/10] drivers base/arch_topology: free cpumask  cpus_to_visit Juri Lelli <juri.lelli@arm.com> - 2017-07-06 13:00 +0200
        Re: [PATCH v2 01/10] drivers base/arch_topology: free cpumask  cpus_to_visit Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 13:20 +0200
          Re: [PATCH v2 01/10] drivers base/arch_topology: free cpumask  cpus_to_visit Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-07 18:00 +0200
  [PATCH v2 10/10] drivers base/arch_topology: inline cpu- and frequency-invariant accounting Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-06 12:00 +0200
    Re: [PATCH v2 10/10] drivers base/arch_topology: inline cpu- and  frequency-invariant accounting Viresh Kumar <viresh.kumar@linaro.org> - 2017-07-06 13:00 +0200
      Re: [PATCH v2 10/10] drivers base/arch_topology: inline cpu- and  frequency-invariant accounting Dietmar Eggemann <dietmar.eggemann@arm.com> - 2017-07-10 17:20 +0200

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