Re: [PATCH v2 06/12] sched: Introduce ttwu_do_migrate()

[Vincent Guittot]

On Wed, 2 Jul 2025 at 14:12, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> Split out the migration related bits into their own function for later
> re-use.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>


> ---
>  kernel/sched/core.c |   26 ++++++++++++++++----------
>  1 file changed, 16 insertions(+), 10 deletions(-)
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3774,6 +3774,21 @@ static int ttwu_runnable(struct task_str
>         return 1;
>  }
>
> +static inline bool ttwu_do_migrate(struct task_struct *p, int cpu)
> +{
> +       if (task_cpu(p) == cpu)
> +               return false;
> +
> +       if (p->in_iowait) {
> +               delayacct_blkio_end(p);
> +               atomic_dec(&task_rq(p)->nr_iowait);
> +       }
> +
> +       psi_ttwu_dequeue(p);
> +       set_task_cpu(p, cpu);
> +       return true;
> +}
> +
>  void sched_ttwu_pending(void *arg)
>  {
>         struct llist_node *llist = arg;
> @@ -4268,17 +4283,8 @@ int try_to_wake_up(struct task_struct *p
>                  * their previous state and preserve Program Order.
>                  */
>                 smp_cond_load_acquire(&p->on_cpu, !VAL);
> -
> -               if (task_cpu(p) != cpu) {
> -                       if (p->in_iowait) {
> -                               delayacct_blkio_end(p);
> -                               atomic_dec(&task_rq(p)->nr_iowait);
> -                       }
> -
> +               if (ttwu_do_migrate(p, cpu))
>                         wake_flags |= WF_MIGRATED;
> -                       psi_ttwu_dequeue(p);
> -                       set_task_cpu(p, cpu);
> -               }
>
>                 ttwu_queue(p, cpu, wake_flags);
>         }
>
>