Re: [PATCH v3 3/6] cpufreq/schedutil: use a fixed reference frequency

[Dietmar Eggemann]

On 18/10/2023 18:25, Vincent Guittot wrote:
> cpuinfo.max_freq can change at runtime because of boost as an example. This
> implies that the value could be different than the one that has been
> used when computing the capacity of a CPU.
> 
> The new arch_scale_freq_ref() returns a fixed and coherent reference
> frequency that can be used when computing a frequency based on utilization.
> 
> Use this arch_scale_freq_ref() when available and fallback to
> policy otherwise.
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> Reviewed-by: Lukasz Luba <lukasz.luba@xxxxxxx>
> Tested-by: Lukasz Luba <lukasz.luba@xxxxxxx>
> 
> ---
>  kernel/sched/cpufreq_schedutil.c | 26 ++++++++++++++++++++++++--
>  1 file changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 458d359f5991..6e4030482ae8 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -114,6 +114,28 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy)
>  	}
>  }
>  
> +/**
> + * cpufreq_get_capacity_ref_freq - get the reference frequency of a given CPU that

s/cpufreq_get_capacity_ref_freq/get_capacity_ref_freq

s/of a given CPU/for a given cpufreq policy ? (of which the CPU managing
it is used for the arch_scale_freq_ref() call in the function.

> + * has been used to correlate frequency and compute capacity.
> + * @policy: the cpufreq policy of the CPU in question.
> + * @use_current: Fallback to current freq instead of policy->cpuinfo.max_freq.

Looks like use_current does not exists as a parameter.

> + *
> + * Return: the reference CPU frequency to compute a capacity.
> + */
> +static __always_inline
> +unsigned long get_capacity_ref_freq(struct cpufreq_policy *policy)
> +{
> +	unsigned int freq = arch_scale_freq_ref(policy->cpu);
> +
> +	if (freq)
> +		return freq;
> +
> +	if (arch_scale_freq_invariant())
> +		return policy->cpuinfo.max_freq;
> +
> +	return policy->cur;
> +}

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>