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SubjectRe: [PATCH] sched: Make schedstats a runtime tunable that is disabled by default v2
On Wed, 27 Jan, at 03:29:26PM, Mel Gorman wrote:
> +#ifdef CONFIG_SCHEDSTATS
> +void set_schedstats(bool enabled)
> +{
> + if (enabled)
> + static_branch_enable(&sched_schedstats);
> + else
> + static_branch_disable(&sched_schedstats);
> +}

This function should probably be 'static'; it has no users outside of
this file.

> @@ -313,17 +317,19 @@ do { \
> #define P(n) SEQ_printf(m, " .%-30s: %d\n", #n, rq->n);
> #define P64(n) SEQ_printf(m, " .%-30s: %Ld\n", #n, rq->n);
>
> - P(yld_count);
> + if (schedstat_enabled()) {
> + P(yld_count);
>
> - P(sched_count);
> - P(sched_goidle);
> + P(sched_count);
> + P(sched_goidle);
> #ifdef CONFIG_SMP
> - P64(avg_idle);
> - P64(max_idle_balance_cost);
> + P64(avg_idle);
> + P64(max_idle_balance_cost);

These two fields are still updated without any kind of
schedstat_enabled() guard. We probably shouldn't refuse to print them
if we're maintaining these counters, right?

> #undef P
> #undef P64
> @@ -569,38 +575,38 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
> nr_switches = p->nvcsw + p->nivcsw;
>
> #ifdef CONFIG_SCHEDSTATS
> - PN(se.statistics.sum_sleep_runtime);
> - PN(se.statistics.wait_start);
> - PN(se.statistics.sleep_start);
> - PN(se.statistics.block_start);
> - PN(se.statistics.sleep_max);
> - PN(se.statistics.block_max);
> - PN(se.statistics.exec_max);
> - PN(se.statistics.slice_max);
> - PN(se.statistics.wait_max);
> - PN(se.statistics.wait_sum);
> - P(se.statistics.wait_count);
> - PN(se.statistics.iowait_sum);
> - P(se.statistics.iowait_count);
> - P(se.nr_migrations);
> - P(se.statistics.nr_migrations_cold);
> - P(se.statistics.nr_failed_migrations_affine);
> - P(se.statistics.nr_failed_migrations_running);
> - P(se.statistics.nr_failed_migrations_hot);
> - P(se.statistics.nr_forced_migrations);
> - P(se.statistics.nr_wakeups);
> - P(se.statistics.nr_wakeups_sync);
> - P(se.statistics.nr_wakeups_migrate);
> - P(se.statistics.nr_wakeups_local);
> - P(se.statistics.nr_wakeups_remote);
> - P(se.statistics.nr_wakeups_affine);
> - P(se.statistics.nr_wakeups_affine_attempts);
> - P(se.statistics.nr_wakeups_passive);
> - P(se.statistics.nr_wakeups_idle);
> -
> - {
> + if (schedstat_enabled()) {
> u64 avg_atom, avg_per_cpu;
>
> + PN(se.statistics.sum_sleep_runtime);
> + PN(se.statistics.wait_start);
> + PN(se.statistics.sleep_start);
> + PN(se.statistics.block_start);
> + PN(se.statistics.sleep_max);
> + PN(se.statistics.block_max);
> + PN(se.statistics.exec_max);
> + PN(se.statistics.slice_max);
> + PN(se.statistics.wait_max);
> + PN(se.statistics.wait_sum);
> + P(se.statistics.wait_count);
> + PN(se.statistics.iowait_sum);
> + P(se.statistics.iowait_count);
> + P(se.nr_migrations);

Ditto for se.nr_migrations. It has no schedstat_enabled() wrapper.

> @@ -801,8 +793,8 @@ static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
> update_stats_wait_start(cfs_rq, se);
> }
>
> -static inline void
> -update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
> +static void
> +update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
> {
> /*
> * Mark the end of the wait period if dequeueing a

You dropped the 'inline' from this function. Since there is only one
caller, I'm guessing that was unintentional?

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