Re: [PATCH] sched/eevdf: fix rb augmented with multi fields

[Vincent Guittot]

On Tue, 8 Sept 2026 at 22:37, K Prateek Nayak <kprateek.nayak@xxxxxxx> wrote:
>
> Hello Vincent,
>
> On 9/8/2026 7:25 PM, Vincent Guittot wrote:
> > The eevdf rb tree maintains 3 augmented fields but only one is currently
> > copied when balancing the tree.
> >
> > Add a more generic define that can be used when there are several augmented
> > fields. In this case, we provide a function that takes care of copying all
> > fields.
> >
> > Fixes: aef6987d8954 ("sched/eevdf: Propagate min_slice up the cgroup hierarchy")
> > Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
>
> I remember stumbling on this in
> https://lore.kernel.org/lkml/20250220093257.9380-22-kprateek.nayak@xxxxxxx/
> but working around the problem in the scheduler layer instead.
>
> Generic rb-tree layer extension makes more sense. Feel free to include:
>
> Reviewed-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
> Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>

Thanks

>
> [..snip.]
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index db5937d7e46e..019812c4fe32 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -1037,6 +1037,16 @@ static inline void __max_slice_update(struct sched_entity *se, struct rb_node *n
> >       }
> >  }
> >
> > +/*
> > + * se->min_vruntime = min(se->vruntime, {left,right}->min_vruntime)
> > + */
>
> nit. Do we need this comment? It doesn't really describe the copy
> callback.

No, it was just the result of a copy/paste

>
> > +static inline void min_vruntime_copy(struct sched_entity *new, struct sched_entity *old)
> > +{
> > +     new->min_vruntime = old->min_vruntime;
> > +     new->min_slice = old->min_slice;
> > +     new->max_slice = old->max_slice;
> > +}
> > +
> >  /*
> >   * se->min_vruntime = min(se->vruntime, {left,right}->min_vruntime)
> >   */
>
> The one over here above min_vruntime_update() makes sense and should
> suffice IMO.
>
> > @@ -1064,8 +1074,9 @@ static inline bool min_vruntime_update(struct sched_entity *se, bool exit)
> >              se->max_slice == old_max_slice;
> >  }
> >
> > -RB_DECLARE_CALLBACKS(static, min_vruntime_cb, struct sched_entity,
> > -                  run_node, min_vruntime, min_vruntime_update);
> > +
> > +RB_DECLARE_CALLBACKS_MULTI(static, min_vruntime_cb, struct sched_entity,
> > +                  run_node, min_vruntime_copy, min_vruntime_update);
> >
> >  /*
> >   * Enqueue an entity into the rb-tree:
>
> --
> Thanks and Regards,
> Prateek
>