On 08/01/2024 14:48, Vincent Guittot 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.
Is this then related to the 'medium pace system pressure' you mentioned
in your OSPM '23 talk?
>
> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> ---
> 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..fa2e2ea26f7f 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;
> +
> + /*
> + * Handle properly the boost frequencies, which should simply clean
> + * the thermal pressure value.
^^^^^^^
IMHO, this is a copy & paste error from topology_update_thermal_pressure()?
> + */
> + if (max_freq <= capped_freq) {
max_freq seems to be uninitialized.
> + pressure = 0;
Is this x86 (turbo boost) specific? IMHO at arm we follow this max freq
(including boost) relates to 1024 in capacity? Or haven't we made this
discussion yet?
> + } else {
> + cpu = cpumask_first(policy->related_cpus);
> + max_capacity = arch_scale_cpu_capacity(cpu);
> + capped_freq = policy->max;
> + max_freq = arch_scale_freq_ref(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);
> +}
> +
[...]
