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

Rafael J. Wysocki
2024-01-09T16:49:54Z

On Tue, Jan 9, 2024 at 5:47 PM 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>

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