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    SubjectRe: [PATCH v2 2/2] sched/cpufreq: Consider reduced CPU capacity in energy calculation
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    On 6/9/21 4:01 PM, Rafael J. Wysocki wrote:
    > On Fri, Jun 4, 2021 at 10:10 AM Lukasz Luba <lukasz.luba@arm.com> wrote:
    >>
    >> Energy Aware Scheduling (EAS) needs to predict the decisions made by
    >> SchedUtil. The map_util_freq() exists to do that.
    >>
    >> There are corner cases where the max allowed frequency might be reduced
    >> (due to thermal). SchedUtil as a CPUFreq governor, is aware of that
    >> but EAS is not. This patch aims to address it.
    >>
    >> SchedUtil stores the maximum allowed frequency in
    >> 'sugov_policy::next_freq' field. EAS has to predict that value, which is
    >> the real used frequency. That value is made after a call to
    >> cpufreq_driver_resolve_freq() which clamps to the CPUFreq policy limits.
    >> In the existing code EAS is not able to predict that real frequency.
    >> This leads to energy estimation errors.
    >>
    >> To avoid wrong energy estimation in EAS (due to frequency miss prediction)
    >> make sure that the step which calculates Performance Domain frequency,
    >> is also aware of the allowed CPU capacity.
    >>
    >> Furthermore, modify map_util_freq() to not extend the frequency value.
    >> Instead, use map_util_perf() to extend the util value in both places:
    >> SchedUtil and EAS, but for EAS clamp it to max allowed CPU capacity.
    >> In the end, we achieve the same desirable behavior for both subsystems
    >> and alignment in regards to the real CPU frequency.
    >>
    >> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
    >
    > For the schedutil part
    >
    > Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    >


    Thank you Rafael!

    Regards,
    Lukasz

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