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SubjectRe: [PATCH v2] kernel/sched: Update schedstats when migrating threads
On Wed, Feb 23, 2022 at 10:13:50AM -0600 Carlos Bilbao wrote:
> The kernel manages per-task scheduler statistics or schedstats. Update
> function migrate_task_to() to increase the counter for migrations.
>
> Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>
> ---
> Changelog:
> v2: Update commit message, don't reinitialize sched fields.
> ---
> kernel/sched/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index fcf0c180617c..1360e501c737 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8751,7 +8751,7 @@ 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 */
> + schedstat_inc(p->stats.nr_migrations_cold);
>

I was going to give a reviewed by since I was looking at this,
but I can't convince myself that nr_migrations_cold is right.
This looks more like a "hot" migration (using stop_cpu to force
it). But nr_migrations_cold is not incremented anywhere else so
maybe it's a terminology thing.

Can you tell me why this is the right counter?


Thanks,
Phil


> trace_sched_move_numa(p, curr_cpu, target_cpu);
> return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
> --
> 2.27.0
>

--

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