Re: [PATCH 2/6] sched/eevdf: Take into account current's lag when updating slice protection

[Vincent Guittot]

On Mon, 15 Jun 2026 at 17:20, Vincent Guittot
<vincent.guittot@xxxxxxxxxx> wrote:
>
> Take into account the lag of current task when setting the slice protection
> in order to ensure that the absolute value of lags will remain in the
> range [0 : slice+tick]
> A task that already has a negative lag will see its protection reduced
> whereas a task with positive lag will keep a full slice protection.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> ---
>  kernel/sched/fair.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 83bce5a04f3d..0b78d8939d07 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1083,6 +1083,7 @@ struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
>   */
>  static inline void set_protect_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  {
> +       u64 vruntime = min(se->vruntime, avg_vruntime(cfs_rq));

should be min_vruntime().
let me fix that


>         u64 slice = normalized_sysctl_sched_base_slice;
>         u64 vprot = se->deadline;
>
> @@ -1090,8 +1091,8 @@ static inline void set_protect_slice(struct cfs_rq *cfs_rq, struct sched_entity
>                 slice = cfs_rq_min_slice(cfs_rq);
>
>         slice = min(slice, se->slice);
> -       if (slice != se->slice)
> -               vprot = min_vruntime(vprot, se->vruntime + calc_delta_fair(slice, se));
> +       if (vruntime != se->vruntime || slice != se->slice)
> +               vprot = min_vruntime(vprot, vruntime + calc_delta_fair(slice, se));
>
>         se->vprot = vprot;
>  }
> @@ -1099,8 +1100,9 @@ static inline void set_protect_slice(struct cfs_rq *cfs_rq, struct sched_entity
>  static inline void update_protect_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  {
>         u64 slice = cfs_rq_min_slice(cfs_rq);
> +       u64 vruntime = min(se->vruntime, avg_vruntime(cfs_rq));

here too

>
> -       se->vprot = min_vruntime(se->vprot, se->vruntime + calc_delta_fair(slice, se));
> +       se->vprot = min_vruntime(se->vprot, vruntime + calc_delta_fair(slice, se));
>  }
>
>  static inline bool protect_slice(struct sched_entity *se)
> --
> 2.43.0
>