linux-kernel - Re: [PATCH v5 3/6] sched/fair: Optimize checking for group_asym

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Message-ID: <CAKfTPtCHFgaWWdxSuRKPrp4cSLA+pTzXAmsGn9N3LrFn0x4B1w@mail.gmail.com>
Date:   Fri, 17 Sep 2021 17:26:26 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Len Brown <len.brown@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        Quentin Perret <qperret@...gle.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        linuxppc-dev@...ts.ozlabs.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Aubrey Li <aubrey.li@...el.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v5 3/6] sched/fair: Optimize checking for group_asym_packing

On Sat, 11 Sept 2021 at 03:19, Ricardo Neri
<ricardo.neri-calderon@...ux.intel.com> wrote:
>
> sched_asmy_prefer() always returns false when called on the local group. By
> checking local_group, we can avoid additional checks and invoking
> sched_asmy_prefer() when it is not needed. No functional changes are
> introduced.
>
> Cc: Aubrey Li <aubrey.li@...el.com>
> Cc: Ben Segall <bsegall@...gle.com>
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Quentin Perret <qperret@...gle.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Tim Chen <tim.c.chen@...ux.intel.com>
> Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> Reviewed-by: Len Brown <len.brown@...el.com>
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>

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

> ---
> Changes since v4:
>   * None
>
> Changes since v3:
>   * Further rewording of the commit message. (Len)
>
> Changes since v2:
>   * Reworded the commit message for clarity. (Peter Z)
>
> Changes since v1:
>   * None
> ---
>  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 ff69f245b939..7a054f528bcc 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8657,7 +8657,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
>         }
>
>         /* Check if dst CPU is idle and preferred to this group */
> -       if (env->sd->flags & SD_ASYM_PACKING &&
> +       if (!local_group && env->sd->flags & SD_ASYM_PACKING &&
>             env->idle != CPU_NOT_IDLE &&
>             sgs->sum_h_nr_running &&
>             sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu)) {
> --
> 2.17.1
>