Hi Peter,
On Wednesday 21 Nov 2018 at 14:08:22 (+0100), Peter Zijlstra wrote:
> On Mon, Nov 19, 2018 at 02:18:51PM +0000, Quentin Perret wrote:
>
> > +static void sched_energy_start(int ndoms_new, cpumask_var_t doms_new[])
> > +{
> > + /*
> > + * The conditions for EAS to start are checked during the creation of
> > + * root domains. If one of them meets all conditions, it will have a
> > + * non-null list of performance domains.
> > + */
> > + while (ndoms_new) {
> > + if (cpu_rq(cpumask_first(doms_new[ndoms_new - 1]))->rd->pd)
> > + goto enable;
> > + ndoms_new--;
> > + }
>
> That seems quite ugly; can't you simply return a bool from
> build_perf_domains() ?
>
> Something like the below, but less fugly ;-)
>
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -299,7 +299,7 @@ static void destroy_perf_domain_rcu(stru
> #define EM_MAX_COMPLEXITY 2048
>
> extern struct cpufreq_governor schedutil_gov;
> -static void build_perf_domains(const struct cpumask *cpu_map)
> +static bool build_perf_domains(const struct cpumask *cpu_map)
> {
> int i, nr_pd = 0, nr_cs = 0, nr_cpus = cpumask_weight(cpu_map);
> struct perf_domain *pd = NULL, *tmp;
> @@ -365,7 +365,7 @@ static void build_perf_domains(const str
> if (tmp)
> call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
>
> - return;
> + return !!pd;
>
> free:
> free_pd(pd);
> @@ -373,6 +373,8 @@ static void build_perf_domains(const str
> rcu_assign_pointer(rd->pd, NULL);
> if (tmp)
> call_rcu(&tmp->rcu, destroy_perf_domain_rcu);
> +
> + return false;
> }
> #else
> static void free_pd(struct perf_domain *pd) { }
> @@ -2173,6 +2175,9 @@ void partition_sched_domains(int ndoms_n
> }
>
> #if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL)
> + {
> + bool has_eas = false;
That one wants to be declared '__maybe_unused' at the top of
partition_sched_domains() perhaps ? Just to avoid the { } section.
Hopefully the compiler will be smart enough to not use stack space for
it if not needed.
> +
> /* Build perf. domains: */
> for (i = 0; i < ndoms_new; i++) {
> for (j = 0; j < n && !sched_energy_update; j++) {
> @@ -2181,10 +2186,13 @@ void partition_sched_domains(int ndoms_n
> goto match3;
And we want to do 'has_eas = true' just before 'goto match3' here.
Otherwise we'll end up disabling EAS if we hit 'goto match3' for all
root domains.
> }
> /* No match - add perf. domains for a new rd */
> - build_perf_domains(doms_new[i]);
> + has_eas |= build_perf_domains(doms_new[i]);
> match3:
> ;
> }
> +
> + sched_energy_set(has_eas);
> + }
> #endif
>
> /* Remember the new sched domains: */
Other than that I guess that should work OK :-)
Thanks,
Quentin
