Re: [PATCH 4/5] sched/debug: remove several CONFIG_SCHEDSTATS guards

From: Peter Zijlstra
Date: Mon Jun 27 2016 - 12:21:21 EST


On Fri, Jun 17, 2016 at 12:43:26PM -0500, Josh Poimboeuf wrote:
> index 017a4f5..0aee5dd 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1626,10 +1626,15 @@ static inline int __set_cpus_allowed_ptr(struct task_struct *p,
> static void
> ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
> {
> -#ifdef CONFIG_SCHEDSTATS
> - struct rq *rq = this_rq();
> + struct rq *rq;
> +
> + if (!schedstat_enabled())
> + return;
> +
> + rq = this_rq();
>
> #ifdef CONFIG_SMP
> +{
> int this_cpu = smp_processor_id();
>
> if (cpu == this_cpu) {
> @@ -1651,7 +1656,7 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
>
> if (wake_flags & WF_MIGRATED)
> schedstat_inc(p->se.statistics.nr_wakeups_migrate);
> -
> +}
> #endif /* CONFIG_SMP */
>
> schedstat_inc(rq->ttwu_count);

I did:

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1636,10 +1636,7 @@ ttwu_stat(struct task_struct *p, int cpu
rq = this_rq();

#ifdef CONFIG_SMP
-{
- int this_cpu = smp_processor_id();
-
- if (cpu == this_cpu) {
+ if (cpu == rq->cpu) {
schedstat_inc(rq->ttwu_local);
schedstat_inc(p->se.statistics.nr_wakeups_local);
} else {
@@ -1647,7 +1644,7 @@ ttwu_stat(struct task_struct *p, int cpu

schedstat_inc(p->se.statistics.nr_wakeups_remote);
rcu_read_lock();
- for_each_domain(this_cpu, sd) {
+ for_each_domain(rq->cpu, sd) {
if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
schedstat_inc(sd->ttwu_wake_remote);
break;
@@ -1658,7 +1655,6 @@ ttwu_stat(struct task_struct *p, int cpu

if (wake_flags & WF_MIGRATED)
schedstat_inc(p->se.statistics.nr_wakeups_migrate);
-}
#endif /* CONFIG_SMP */

schedstat_inc(rq->ttwu_count);