Re: [PATCH] kernel/sched: Update schedstats when migrating threads

From: Carlos Bilbao
Date: Tue Feb 22 2022 - 11:33:49 EST


Hi,

On 1/26/2022 9:22 AM, Carlos Bilbao wrote:
> The kernel manages per-task scheduler statistics or schedstats. Such
> counters should be reinitialized when the thread is migrated to a
> different core rq, except for the values recording number of migrations.
>
> Signed-off-by: Carlos Bilbao <carlos.bilbao@xxxxxxx>
> ---
> kernel/sched/core.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index fe53e510e711..d64c2a290176 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8757,6 +8757,7 @@ bool sched_smp_initialized __read_mostly;
> int migrate_task_to(struct task_struct *p, int target_cpu)
> {
> struct migration_arg arg = { p, target_cpu };
> + uint64_t forced_migrations, migrations_cold;
> int curr_cpu = task_cpu(p);
>
> if (curr_cpu == target_cpu)
> @@ -8765,7 +8766,14 @@ int migrate_task_to(struct task_struct *p, int target_cpu)
> if (!cpumask_test_cpu(target_cpu, p->cpus_ptr))
> return -EINVAL;
>
> - /* TODO: This is not properly updating schedstats */
> + if (schedstat_enabled()) {
> + forced_migrations = schedstat_val(p->stats.nr_forced_migrations);
> + migrations_cold = schedstat_val(p->stats.nr_migrations_cold);
> + memset(&p->stats, 0, sizeof(p->stats));
> + schedstat_set(p->stats.nr_forced_migrations, forced_migrations);
> + schedstat_set(p->stats.nr_migrations_cold, migrations_cold);
> + schedstat_inc(p->stats.nr_migrations_cold);
> + }
>
> trace_sched_move_numa(p, curr_cpu, target_cpu);
> return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);


I would love to hear some thoughts on this.

Thanks,
Carlos