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Re: [PATCH v3 0/3] cpufreq: avoid redundant driver calls in schedutil

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On 13-07-16, 13:25, Steve Muckle wrote:
> Invoking the cpufreq driver to set a frequency can be expensive. On platforms
> with a cpufreq driver that does not support fast switching a thread must be
> woken to complete the operation. IPIs will also occur if and when support to
> process remote task wakeups is added in schedutil.
> 
> Currently schedutil calculates a raw frequency request from scheduler
> utilization data. This raw frequency request does not correlate to supported
> cpufreq driver frequencies aside from being capped by the CPU's maximum
> frequency. Consequently, there may be many consecutive requests for different
> raw frequency values which all translate to the same driver-supported
> frequency. For example on a platform with 3 supported frequencies 200MHz,
> 400MHz, and 600MHz, raw requests for 257MHz, 389MHz, and 307MHz all map to a
> driver-supported frequency of 400MHz in schedutil. Assuming these requests were
> consecutive and there were no changes in policy limits (min/max), there is no
> need to issue the second or third request.
> 
> In order to resolve a raw frequency request to a driver-supported one a new
> cpufreq API is added, cpufreq_driver_resolve_freq(). This API relies on a new
> cpufreq driver callback in the case of ->target() style drivers. Otherwise it
> uses the existing frequency table operations.
> 
> Lookups are cached both in cpufreq_driver_resolve_freq() (for the benefit of the
> driver) and in schedutil.
> 
> Changes since v2:
> - incorporated feedback from Viresh to use resolve_freq driver callbacks
>   only for ->target() style drivers, to use cpufreq's freq table operations,
>   and move freq mapping caching into cpufreq policy

Sorry for the delay buddy :(

I have some concerns for the first patch. The second and third patch
look fine.  Feel free to add my 

Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>

for them.

-- 
viresh

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[PATCH v3 0/3] cpufreq: avoid redundant driver calls in schedutil Steve Muckle <steve.muckle@linaro.org> - 2016-07-13 22:30 +0200
  [PATCH v3 3/3] cpufreq: acpi-cpufreq: use cached frequency mapping when possible Steve Muckle <steve.muckle@linaro.org> - 2016-07-13 22:30 +0200
  [PATCH v3 2/3] cpufreq: schedutil: map raw required frequency to driver frequency Steve Muckle <steve.muckle@linaro.org> - 2016-07-13 22:30 +0200
  [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Steve Muckle <steve.muckle@linaro.org> - 2016-07-13 22:30 +0200
    Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-21 22:00 +0200
      Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-21 22:30 +0200
        Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-21 22:40 +0200
          Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-21 22:50 +0200
            Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-21 23:00 +0200
              Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-21 23:20 +0200
              Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-07-21 23:20 +0200
          Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Steve Muckle <steve.muckle@linaro.org> - 2016-07-22 01:30 +0200
            Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-22 01:40 +0200
              Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Steve Muckle <steve.muckle@linaro.org> - 2016-07-22 01:40 +0200
                Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Steve Muckle <steve.muckle@linaro.org> - 2016-07-22 01:50 +0200
                Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Steve Muckle <steve.muckle@linaro.org> - 2016-07-22 02:50 +0200
                Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-22 17:20 +0200
                Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Steve Muckle <steve.muckle@linaro.org> - 2016-07-22 19:50 +0200
            Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-22 01:40 +0200
            Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Steve Muckle <steve.muckle@linaro.org> - 2016-07-22 01:40 +0200
    Re: [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-21 23:20 +0200
  Re: [PATCH v3 0/3] cpufreq: avoid redundant driver calls in schedutil Pingbo Wen <pingbo.wen@linaro.org> - 2016-07-14 12:10 +0200
    Re: [PATCH v3 0/3] cpufreq: avoid redundant driver calls in schedutil Steve Muckle <steve.muckle@linaro.org> - 2016-07-14 20:10 +0200
  Re: [PATCH v3 0/3] cpufreq: avoid redundant driver calls in schedutil Viresh Kumar <viresh.kumar@linaro.org> - 2016-07-21 22:10 +0200

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