Re: [PATCH v2 2/3] sched/fair: util_est: update before schedutil

[Vincent Guittot]

Hi Patrick,

On 11 May 2018 at 15:15, Patrick Bellasi <patrick.bellasi@xxxxxxx> wrote:
> When a task is enqueue the estimated utilization of a CPU is updated
> to better support the selection of the required frequency.
> However, schedutil is (implicitly) updated by update_load_avg() which
> always happens before util_est_{en,de}queue(), thus potentially
> introducing a latency between estimated utilization updates and
> frequency selections.
>
> Let's update util_est at the beginning of enqueue_task_fair(),
> which will ensure that all schedutil updates will see the most
> updated estimated utilization value for a CPU.
>
> Reported-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> Signed-off-by: Patrick Bellasi <patrick.bellasi@xxxxxxx>
> Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-pm@xxxxxxxxxxxxxxx
> Fixes: 7f65ea42eb00 ("sched/fair: Add util_est on top of PELT")

Acked-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>

>
> ---
>
> Changes in v2:
>  - improve comment in enqueue_task_fair() (Peter)
>  - add "Fixes" tag
>  - add "Acked-by" Viresh tag
> ---