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Message-ID: <bd755dd1-0326-e0e0-6730-a41ba46bbd6e@arm.com>
Date: Mon, 5 Aug 2019 12:01:16 +0100
From: Valentin Schneider <valentin.schneider@....com>
To: Vincent Guittot <vincent.guittot@...aro.org>,
linux-kernel@...r.kernel.org, mingo@...hat.com,
peterz@...radead.org
Cc: pauld@...hat.com, srikar@...ux.vnet.ibm.com,
quentin.perret@....com, dietmar.eggemann@....com,
Morten.Rasmussen@....com
Subject: Re: [PATCH v3] sched/fair: use utilization to select misfit task
On 02/08/2019 13:56, Vincent Guittot wrote:
> utilization is used to detect a misfit task but the load is then used to
> select the task on the CPU which can lead to select a small task with
> high weight instead of the task that triggered the misfit migration.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
> Keep tracking load instead of utilization but check that
> task doesn't fit CPU's capacity when selecting the task to detach as
> suggested by Valentin
>
> kernel/sched/fair.c | 12 +++---------
> 1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 53e64a7..8496118 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7487,15 +7487,9 @@ static int detach_tasks(struct lb_env *env)
> break;
>
> case migrate_misfit:
> - load = task_h_load(p);
> -
> - /*
> - * utilization of misfit task might decrease a bit
> - * since it has been recorded. Be conservative in the
> - * condition.
> - */
> - if (load < env->imbalance)
> - goto next;
> + /* This is not a misfit task */
> + if (task_fits_capacity(p, capacity_of(env->src_cpu)))
^^^^^^^^^^^^^^^^^^^^^^^
Just noticed those are spaces for some reason (I think my original diff is
to blame)
> + goto next;
>
> env->imbalance = 0;
> break;
>
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