Re: [PATCH v3 03/10] sched/fair: Credit queued next-buddy via canonical requeue

[Vincent Guittot]

On Fri, 12 Jun 2026 at 03:34, Wanpeng Li <kernellwp@xxxxxxxxx> wrote:
>
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> eevdf_credit_entity_vlag() handles cfs_rq->curr, which is off-tree. Extend
> it to a queued entity, which is the common case when yield_to() targets a
> task that is runnable but not currently executing.
>
> A queued entity's key contributes to cfs_rq->sum_w_vruntime, so its
> vruntime cannot be shifted in place. Use the canonical place_entity()-
> paired requeue pattern: snapshot vlag, make the deadline relative to
> se->vruntime, dequeue the entity, apply the credit via place_entity(), and
> enqueue it again. This keeps sum_w_vruntime consistent with entity_key(),
> preserves the slice, and shifts the deadline by the same amount as the
> off-tree current-entity path.
>
> The helper is not called in this change; there is no functional change.

Merge this patch with the 2 previous ones. I don't see the benefit of
split it in 3 different patches

>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
>  kernel/sched/fair.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index c6502db62cd3..c28682fedb36 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9372,7 +9372,9 @@ eevdf_persistent_margin(struct cfs_rq *cfs_rq, struct sched_entity *se)
>   * to a bounded positive-vlag margin so pick_eevdf()'s PICK_BUDDY branch
>   * keeps returning it across several picks, without exceeding entity_lag()'s
>   * legal bound. cfs_rq->curr is shifted in place (off-tree, carrying any
> - * vprot window). Queued entities are left unchanged.
> + * vprot window); a queued entity uses the canonical
> + * place_entity()-paired requeue, keeping sum_w_vruntime consistent with
> + * entity_key().
>   *
>   * Idempotent once @se holds the margin. Caller must hold
>   * rq_of(cfs_rq)->lock with rq_clock up to date.
> @@ -9422,7 +9424,22 @@ eevdf_credit_entity_vlag(struct cfs_rq *cfs_rq, struct sched_entity *se)
>                 return;
>         }
>
> -       /* Queued entities are left unchanged by this helper path. */
> +       /*
> +        * Canonical place_entity()-paired requeue: see dequeue_entity() and
> +        * requeue_delayed_entity(). place_entity() restores the deadline via
> +        * "se->deadline += se->vruntime", so make the deadline relative to
> +        * se->vruntime here (not avg_vruntime). This preserves the slice and
> +        * shifts the deadline by exactly -credit, mirroring the curr branch
> +        * and keeping deadline > vruntime.
> +        */
> +       se->vlag = vlag + (s64)credit;
> +       se->deadline -= se->vruntime;
> +       se->rel_deadline = 1;
> +       cfs_rq->nr_queued--;
> +       __dequeue_entity(cfs_rq, se);
> +       place_entity(cfs_rq, se, 0);
> +       __enqueue_entity(cfs_rq, se);
> +       cfs_rq->nr_queued++;
>  }
>
>  /*
> --
> 2.43.0
>