Re: [RFC PATCH v3 2/6] sched/cpufreq: Attach perf domain to sugov policy

[Douglas Raillard]

Hi Dietmar,

On 10/17/19 9:57 AM, Dietmar Eggemann wrote:
> On 11/10/2019 15:44, Douglas RAILLARD wrote:
>
> [...]
>
> > @@ -66,6 +70,38 @@ static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);
> >   
> >   /************************ Governor internals ***********************/
> >   
> > +#ifdef CONFIG_ENERGY_MODEL
> > +static void sugov_policy_attach_pd(struct sugov_policy *sg_policy)
> > +{
> > +	struct em_perf_domain *pd;
> > +	struct cpufreq_policy *policy = sg_policy->policy;
>
> Shouldn't always order local variable declarations from longest to
> shortest line?

Can't find any reference to that rule in the coding style, although I'm happy to change order
if that's deemed useful.

> > +
> > +	sg_policy->pd = NULL;
> > +	pd = em_cpu_get(policy->cpu);
> > +	if (!pd)
> > +		return;
> > +
> > +	if (cpumask_equal(policy->related_cpus, to_cpumask(pd->cpus)))
> > +		sg_policy->pd = pd;
> > +	else
> > +		pr_warn("%s: Not all CPUs in schedutil policy %u share the same perf domain, no perf domain for that policy will be registered\n",
> > +			__func__, policy->cpu);
>
> Maybe {} because of 2 lines?

+1

> > +}
> > +
> > +static struct em_perf_domain *sugov_policy_get_pd(
> > +						struct sugov_policy *sg_policy)
>
>
> Maybe this way? This format is already used in this file.
>
> static struct em_perf_domain *
> sugov_policy_get_pd(struct sugov_policy *sg_policy)

I also prefer this kind of non-indented form that always stays indented across renames :)

> > +{
> > +	return sg_policy->pd;
> > +}
> > +#else /* CONFIG_ENERGY_MODEL */
> > +static void sugov_policy_attach_pd(struct sugov_policy *sg_policy) {}
> > +static struct em_perf_domain *sugov_policy_get_pd(
> > +						struct sugov_policy *sg_policy)
> > +{
> > +	return NULL;
> > +}
> > +#endif /* CONFIG_ENERGY_MODEL */
> > +
> >   static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
> >   {
> >   	s64 delta_ns;
> > @@ -859,6 +895,9 @@ static int sugov_start(struct cpufreq_policy *policy)
> >   							sugov_update_shared :
> >   							sugov_update_single);
> >   	}
> > +
> > +	sugov_policy_attach_pd(sg_policy);
> > +
> >   	return 0;
> >   }
>
> A sugov_policy_detach_pd() called from sugov_stop() (doing for instance
> the g_policy->pd = NULL) is not needed?

From what I could see, sugov_stop() will always be followed by sugov_start() before
it's used again, so that does not seem more risky than not de-initializing sg_cpu's
for example.