Re: [PATCH v1] cpufreq: Make cpufreq_update_pressure() fall back to cpuinfo.max_freq

[Viresh Kumar]

On 07-07-26, 19:25, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> 
> If arch_scale_freq_ref() is not defined for a given arch (like x86, for
> example), cpufreq_update_pressure() will always set cpufreq_pressure to
> zero for all CPUs in the system, which is generally problematic on
> systems with asymmetric capacity [1].
> 
> However, in the absence of arch_scale_freq_ref(), it is reasonable
> to assume that cpuinfo.max_freq is the maximum sustainable frequency
> for the given cpufreq policy.  Moreover, there are cases in which
> arch_scale_freq_ref() would need to be defined to return essentially
> the cpuinfo.max_freq value anyway (for example, intel_pstate on
> hybrid platforms).
> 
> For the above reasons, update cpufreq_update_pressure() to fall back to
> using cpuinfo.max_freq as the reference frequency if zero is returned by
> arch_scale_freq_ref().
> 
> Fixes: 75d659317bb1 ("cpufreq: Add a cpufreq pressure feedback for the scheduler")
> Link: https://lore.kernel.org/lkml/CAKfTPtBuRLfYNnR4w--cFZYZy-R8gaPEgVwCcaMmbCcJ2H-muQ@xxxxxxxxxxxxxx/ [1]
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
>  drivers/cpufreq/cpufreq.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2590,6 +2590,9 @@ static void cpufreq_update_pressure(stru
>  
>  	cpu = cpumask_first(policy->related_cpus);
>  	max_freq = arch_scale_freq_ref(cpu);
> +	if (!max_freq)
> +		max_freq = policy->cpuinfo.max_freq;
> +
>  	capped_freq = policy->max;
>  
>  	/*

Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>

-- 
viresh