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SubjectRe: [PATCH v9 09/15] sched: Introduce sched_energy_present static key
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;
+
/* 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;
}
/* 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: */
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