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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Mon, 11 Dec 2023 20:52:37 +0100
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Subject: Re: [PATCH v7 0/7] consolidate and cleanup CPU capacity
To:     Vincent Guittot <vincent.guittot@linaro.org>
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On Mon, Dec 11, 2023 at 11:49 AM Vincent Guittot
<vincent.guittot@linaro.org> wrote:
>
> This is the 1st part of consolidating how the max compute capacity is
> used in the scheduler and how we calculate the frequency for a level of
> utilization.
>
> Fix some unconsistancy when computing frequency for an utilization. There
> can be a mismatch between energy model and schedutil.
>
> Next step will be to make a difference between the original
> max compute capacity of a CPU and what is currently available when
> there is a capping applying forever (i.e. seconds or more).
>
> Changes since v6:
> - Rebase on tip/sched/core and fix a conflict
> - Add tags
>
> Changes since v5:
> - Remove useless return in freq_inv_set_max_ratio()
> - Add tags
>
> Changes since v4:
> - Capitalize the verb in subject
> - Remove usless parentheses in cppc_get_dmi_max_khz()
> - Use freq_ref pattern everywhere
> - Fix MHz / kHz units conversion for cppc_cpufreq
> - Move default definition of arch_scale_freq_ref() in
>   include/linux/sched/topology.h beside arch_scale_cpu_capacity
>   which faces similar default declaration behavior. This location covers
>   all cases with arch and CONFIG_* which was not the case with previous
>   attempts.
>
> Changes since v3:
> - Split patch 5 cpufreq/cppc
> - Fix topology_init_cpu_capacity_cppc()
> - Fix init if AMU ratio
> - Added some tags
>
> Changes since v2:
> - Remove the 1st patch which has been queued in tip
> - Rework how to initialize the reference frequency for cppc_cpufreq and
>   change topology_init_cpu_capacity_cppc() to also set capacity_ref_freq
> - Add a RFC to convert AMU to use arch_scale_freq_ref and move the config
>   of the AMU ratio to be done when intializing cpu capacity and
>   capacity_ref_freq
> - Added some tags
>
> Changes since v1:
> - Fix typos
> - Added changes in cpufreq to use arch_scale_freq_ref() when calling
>   arch_set_freq_scale (patch 3).
> - arch_scale_freq_ref() is always defined and returns 0 (as proposed
>   by Ionela) when not defined by the arch. This simplifies the code with
>   the addition of patch 3.
> - Simplify Energy Model which always uses arch_scale_freq_ref(). The
>   latter returns 0 when not defined by arch instead of last item of the
>   perf domain. This is not a problem because the function is only defined
>   for compilation purpose in this case and we don't care about the
>   returned value. (patch 5)
> - Added changes in cppc cpufreq to set capacity_ref_freq (patch 6)
> - Added reviewed tag for patch 1 which got a minor change but not for
>   others as I did some changes which could make previous reviewed tag
>   no more relevant.
>
> Vincent Guittot (7):
>   topology: Add a new arch_scale_freq_reference
>   cpufreq: Use the fixed and coherent frequency for scaling capacity
>   cpufreq/schedutil: Use a fixed reference frequency
>   energy_model: Use a fixed reference frequency
>   cpufreq/cppc: Move and rename cppc_cpufreq_{perf_to_khz|khz_to_perf}
>   cpufreq/cppc: Set the frequency used for computing the capacity
>   arm64/amu: Use capacity_ref_freq to set AMU ratio

This series touches multiple places, but mostly schedutil, cpufreq and
the EM, so please let me know if you want me to pick it up.