Re: [PATCH v2 1/7] sched/fair: Fix zero_vruntime tracking

[John Stultz]

On Mon, Mar 30, 2026 at 3:10 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> This means, that if the two tasks playing leapfrog can reach the
> critical speed to reach the overflow point inside one tick's worth of
> time, we're up a creek.
>
> If this is indeed the case, then the below should cure things.
>
> This also means that running a HZ=100 config will increase the chances
> of hitting this vs HZ=1000.
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 9298f49f842c..c7daaf941b26 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9307,6 +9307,7 @@ static void yield_task_fair(struct rq *rq)
>         if (entity_eligible(cfs_rq, se)) {
>                 se->vruntime = se->deadline;
>                 se->deadline += calc_delta_fair(se->slice, se);
> +               avg_vruntime(cfs_rq);
>         }
>  }

I just tested with this and similar to Prateek, I also still tripped the issue.

I'll give your new patch a spin here in a second.

thanks
-john