Received-SPF: pass (google.com: domain of linux-kernel+bounces-51611-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Precedence: bulk
MIME-Version: 1.0
References: <20240204044618.46100-1-void@manifault.com> <20240204044618.46100-3-void@manifault.com>
In-Reply-To: <20240204044618.46100-3-void@manifault.com>
From: Vincent Guittot <vincent.guittot@linaro.org>
Date: Sun, 4 Feb 2024 12:45:18 +0100
Message-ID: <CAKfTPtCGfUSa4trbCPnbhDqwqM9jL-qpfg=_E6G9amRuhm4NHg@mail.gmail.com>
Subject: Re: [PATCH v2 2/3] sched/fair: Do strict inequality check for busiest
 misfit task group
To: David Vernet <void@manifault.com>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, 
	juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, 
	bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, 
	kernel-team@meta.com
Content-Type: text/plain; charset="UTF-8"

On Sun, 4 Feb 2024 at 05:46, David Vernet <void@manifault.com> wrote:
>
> In update_sd_pick_busiest(), when comparing two sched groups that are
> both of type group_misfit_task, we currently consider the new group as
> busier than the current busiest group even if the new group has the
> same misfit task load as the current busiest group. We can avoid some
> unnecessary writes if we instead only consider the newest group to be
> the busiest if it has a higher load than the current busiest. This
> matches the behavior of other group types where we compare load, such as
> two groups that are both overloaded.
>
> Let's update the group_misfit_task type comparison to also only update
> the busiest group in the event of strict inequality.

fair enough

Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>

>
> Signed-off-by: David Vernet <void@manifault.com>
> ---
>  kernel/sched/fair.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e7519ea434b1..76d03106040d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -10028,7 +10028,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
>                  * If we have more than one misfit sg go with the biggest
>                  * misfit.
>                  */
> -               if (sgs->group_misfit_task_load < busiest->group_misfit_task_load)
> +               if (sgs->group_misfit_task_load <= busiest->group_misfit_task_load)
>                         return false;
>                 break;
>
> --
> 2.43.0
>