linux-kernel - Re: [PATCH v4 1/5] cpufreq: Add a cpufreq pressure feedback for the scheduler

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Message-ID: <CAJZ5v0ixmEiOhwBHkDqH8QNtchiszAEi0rY2pDCGHXiWHob0NA@mail.gmail.com>
Date: Tue, 9 Jan 2024 17:49:42 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: linux@...linux.org.uk, catalin.marinas@....com, will@...nel.org, 
	sudeep.holla@....com, rafael@...nel.org, viresh.kumar@...aro.org, 
	agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org, 
	mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com, 
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, 
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	rui.zhang@...el.com, mhiramat@...nel.org, daniel.lezcano@...aro.org, 
	amit.kachhap@...il.com, corbet@....net, gregkh@...uxfoundation.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
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	qyousef@...alina.io
Subject: Re: [PATCH v4 1/5] cpufreq: Add a cpufreq pressure feedback for the scheduler

On Tue, Jan 9, 2024 at 5:47 PM Vincent Guittot
<vincent.guittot@...aro.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@...aro.org>

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

and I think I've given the tag on this patch already.

> ---
>  drivers/cpufreq/cpufreq.c | 36 ++++++++++++++++++++++++++++++++++++
>  include/linux/cpufreq.h   | 10 ++++++++++
>  2 files changed, 46 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 44db4f59c4cc..f4eee3d107f1 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2563,6 +2563,40 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, 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 = cpumask_first(policy->related_cpus);
> +       max_freq = arch_scale_freq_ref(cpu);
> +       capped_freq = policy->max;
> +
> +       /*
> +        * Handle properly the boost frequencies, which should simply clean
> +        * the cpufreq pressure value.
> +        */
> +       if (max_freq <= capped_freq) {
> +               pressure = 0;
> +       } else {
> +               max_capacity = arch_scale_cpu_capacity(cpu);
> +               pressure = max_capacity -
> +                          mult_frac(max_capacity, capped_freq, max_freq);
> +       }
> +
> +       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 +2652,8 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
>         policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
>         trace_cpu_frequency_limits(policy);
>
> +       cpufreq_update_pressure(policy);
> +
>         policy->cached_target_freq = 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 cpufreq_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
>