Re: [PATCH 4/4] energy_model: use a fixed reference frequency

[Dietmar Eggemann <dietmar.eggemann@arm.com>]

On 01/09/2023 15:03, Vincent Guittot wrote:

[...]

> diff --git a/include/linux/energy_model.h b/include/linux/energy_model.h
> index b9caa01dfac4..7ee07be6928e 100644
> --- a/include/linux/energy_model.h
> +++ b/include/linux/energy_model.h
> @@ -204,6 +204,20 @@ struct em_perf_state *em_pd_get_efficient_state(struct em_perf_domain *pd,
>  	return ps;
>  }
>  
> +#ifdef arch_scale_freq_ref
> +static __always_inline
> +unsigned long  arch_scale_freq_ref_em(int cpu, struct em_perf_domain *pd)

Why is this function named with the arch prefix?

So far we have 5 arch functions (arch_scale_freq_tick() <->
arch_scale_freq_ref()) and e.g. Arm/Arm64 defines them with there
topology_foo implementations.

Isn't arch_scale_freq_ref_em() (as well as arch_scale_freq_ref_policy())
different in this sense and so a proper EM function which should
manifest in its name?

> +{
> +	return arch_scale_freq_ref(cpu);
> +}
> +#else
> +static __always_inline
> +unsigned long  arch_scale_freq_ref_em(int cpu, struct em_perf_domain *pd)
> +{
> +	return pd->table[pd->nr_perf_states - 1].frequency;
> +}
> +#endif

[...]

> @@ -241,11 +255,11 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
>  	 */
>  	cpu = cpumask_first(to_cpumask(pd->cpus));
>  	scale_cpu = arch_scale_cpu_capacity(cpu);
> -	ps = &pd->table[pd->nr_perf_states - 1];
> +	ref_freq = arch_scale_freq_ref_em(cpu, pd);

Why not using existing `unsigned long freq` here like in schedutil's
get_next_freq()?

>  
>  	max_util = map_util_perf(max_util);

[...]