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References: <20231221152407.436177-1-vincent.guittot@linaro.org> <20231221152407.436177-2-vincent.guittot@linaro.org>
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From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: Thu, 21 Dec 2023 20:57:08 +0100
Message-ID: <CAJZ5v0iU+nx_Tk_K74=dfeOuA7Lyvbq51UW=U1L4mZVEKy-+ZQ@mail.gmail.com>
Subject: Re: [PATCH v2 1/5] cpufreq: Add a cpufreq pressure feedback for the scheduler
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: catalin.marinas@arm.com, will@kernel.org, sudeep.holla@arm.com, 
	rafael@kernel.org, viresh.kumar@linaro.org, agross@kernel.org, 
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On Thu, Dec 21, 2023 at 4:24=E2=80=AFPM Vincent Guittot
<vincent.guittot@linaro.org> wrote:
>
> Provide to the scheduler a feedback about the temporary max available
> capacity. Unlike arch_update_thermal_pressure, this doesn't need to be
> filtered as the pressure will happen for dozens ms or more.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 34 ++++++++++++++++++++++++++++++++++
>  include/linux/cpufreq.h   | 10 ++++++++++
>  2 files changed, 44 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 44db4f59c4cc..15bd41f9bb5e 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2563,6 +2563,38 @@ int cpufreq_get_policy(struct cpufreq_policy *poli=
cy, unsigned int cpu)
>  }
>  EXPORT_SYMBOL(cpufreq_get_policy);
>
> +DEFINE_PER_CPU(unsigned long, cpufreq_pressure);
> +
> +/**
> + * cpufreq_update_pressure() - Update cpufreq pressure for CPUs
> + * @policy: cpufreq policy of the CPUs.
> + *
> + * Update the value of cpufreq pressure for all @cpus in the policy.
> + */
> +static void cpufreq_update_pressure(struct cpufreq_policy *policy)
> +{
> +       unsigned long max_capacity, capped_freq, pressure;
> +       u32 max_freq;
> +       int cpu;
> +
> +       cpu =3D cpumask_first(policy->related_cpus);
> +       pressure =3D max_capacity =3D arch_scale_cpu_capacity(cpu);

I would prefer two separate statements instead of the above.

Other than this

Acked-by: Rafael J. Wysocki <rafael@kernel.org>

> +       capped_freq =3D policy->max;
> +       max_freq =3D arch_scale_freq_ref(cpu);
> +
> +       /*
> +        * Handle properly the boost frequencies, which should simply cle=
an
> +        * the thermal pressure value.
> +        */
> +       if (max_freq <=3D capped_freq)
> +               pressure -=3D max_capacity;
> +       else
> +               pressure -=3D mult_frac(max_capacity, capped_freq, max_fr=
eq);
> +
> +       for_each_cpu(cpu, policy->related_cpus)
> +               WRITE_ONCE(per_cpu(cpufreq_pressure, cpu), pressure);
> +}
> +
>  /**
>   * cpufreq_set_policy - Modify cpufreq policy parameters.
>   * @policy: Policy object to modify.
> @@ -2618,6 +2650,8 @@ static int cpufreq_set_policy(struct cpufreq_policy=
 *policy,
>         policy->max =3D __resolve_freq(policy, policy->max, CPUFREQ_RELAT=
ION_H);
>         trace_cpu_frequency_limits(policy);
>
> +       cpufreq_update_pressure(policy);
> +
>         policy->cached_target_freq =3D UINT_MAX;
>
>         pr_debug("new min and max freqs are %u - %u kHz\n",
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index afda5f24d3dd..b1d97edd3253 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -241,6 +241,12 @@ struct kobject *get_governor_parent_kobj(struct cpuf=
req_policy *policy);
>  void cpufreq_enable_fast_switch(struct cpufreq_policy *policy);
>  void cpufreq_disable_fast_switch(struct cpufreq_policy *policy);
>  bool has_target_index(void);
> +
> +DECLARE_PER_CPU(unsigned long, cpufreq_pressure);
> +static inline unsigned long cpufreq_get_pressure(int cpu)
> +{
> +       return per_cpu(cpufreq_pressure, cpu);
> +}
>  #else
>  static inline unsigned int cpufreq_get(unsigned int cpu)
>  {
> @@ -263,6 +269,10 @@ static inline bool cpufreq_supports_freq_invariance(=
void)
>         return false;
>  }
>  static inline void disable_cpufreq(void) { }
> +static inline unsigned long cpufreq_get_pressure(int cpu)
> +{
> +       return 0;
> +}
>  #endif
>
>  #ifdef CONFIG_CPU_FREQ_STAT
> --
> 2.34.1
>