Re: [RFC PATCH v2 4/6] sched/fair: Introduce an energy estimation helper function

[Peter Zijlstra]

On Fri, Apr 06, 2018 at 04:36:05PM +0100, Dietmar Eggemann wrote:
> +static inline
> +struct capacity_state *find_cap_state(int cpu, unsigned long util)
> +{
> +	struct sched_energy_model *em = *per_cpu_ptr(energy_model, cpu);
> +	struct capacity_state *cs = NULL;
> +	int i;
> +
> +	util += util >> 2;
> +
> +	for (i = 0; i < em->nr_cap_states; i++) {
> +		cs = &em->cap_states[i];
> +		if (cs->cap >= util)
> +			break;
> +	}
> +
> +	return cs;
> +}

So in the last thread there was some discussion about this; in
particular on how this related to schedutil and if we should tie it into
that.

I think for starters tying it to schedutil is not a bad idea; ideally
people _should_ migrate towards using that.

Also; I think it makes sense to better integrate cpufreq and the
energy-model values like what rjw already suggested, such that maybe we
can have cpufreq_driver_resolve_freq() return a structure containing the
relevant information for the selected frequency.

But implementing the frequency selection thing in multiple places like
now sounds like a very bad idea to me.