Re: [PATCH 2/4 v2] sched/fair: reduce minimal imbalance threshold

[Valentin Schneider]

On 21/09/20 08:24, Vincent Guittot wrote:
> The 25% default imbalance threshold for DIE and NUMA domain is large
> enough to generate significant unfairness between threads. A typical
> example is the case of 11 threads running on 2x4 CPUs. The imbalance of
> 20% between the 2 groups of 4 cores is just low enough to not trigger
> the load balance between the 2 groups. We will have always the same 6
> threads on one group of 4 CPUs and the other 5 threads on the other
> group of CPUS. With a fair time sharing in each group, we ends up with
> +20% running time for the group of 5 threads.
>
> Consider decreasing the imbalance threshold for overloaded case where we
> use the load to balance task and to ensure fair time sharing.
>
> Acked-by: Hillf Danton <hdanton@xxxxxxxx>
> Reviewed-by: Phil Auld <pauld@xxxxxxxxxx>
> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>

Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx>