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

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