Re: [PATCH v4 7/7] cpufreq: schedutil: New governor based on scheduler utilization data

[Peter Zijlstra]

On Wed, Mar 16, 2016 at 03:59:18PM +0100, Rafael J. Wysocki wrote:

> +static unsigned int get_next_freq(struct cpufreq_policy *policy,
> +                               unsigned long util, unsigned long max)
> +{
> +     unsigned int freq = arch_scale_freq_invariant() ?
> +                             policy->cpuinfo.max_freq : policy->cur;
> +
> +     return (freq + (freq >> 2)) * util / max;
> +}
> +
> +static void sugov_update_single(struct update_util_data *hook, u64 time,
> +                             unsigned long util, unsigned long max)
> +{
> +     struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, 
> update_util);
> +     struct sugov_policy *sg_policy = sg_cpu->sg_policy;
> +     struct cpufreq_policy *policy = sg_policy->policy;
> +     unsigned int next_f;
> +
> +     if (!sugov_should_update_freq(sg_policy, time))
> +             return;
> +
> +     next_f = util <= max ?
> +             get_next_freq(policy, util, max) : policy->cpuinfo.max_freq;

I'm not sure that is correct, would not something like this be more
accurate?

        if (util > max)
                util = max;
        next_f = get_next_freq(policy, util, max);

After all, if we clip util we will still only increment to the next freq
with our multiplication factor.

Hmm, or was this meant to deal with the DL/RT stuff?

Would then not something like:

        /* ULONG_MAX is used to force max_freq for Real-Time policies */
        if (util == ULONG_MAX) {
                next_f = policy->cpuinfo.max_freq;
        } else {
                if (util > max)
                        util = max;
                next_f = get_next_freq(policy, util, max);
        }

Be clearer?

> +     sugov_update_commit(sg_policy, time, next_f);
> +}