linux-kernel - Re: [PATCH 1/2] sched/fair: Remove redundant lookup of rq in check_preempt

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Date:   Tue, 21 Sep 2021 09:21:16 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] sched/fair: Remove redundant lookup of rq in check_preempt_wakeup

On Mon, 20 Sept 2021 at 16:26, Mel Gorman <mgorman@...hsingularity.net> wrote:
>
> The rq for curr is read during the function preamble, remove the
> redundant lookup.
>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
> ---
>  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..038edfaaae9e 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7190,7 +7190,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
>         if (cse_is_idle != pse_is_idle)
>                 return;
>
> -       update_curr(cfs_rq_of(se));
> +       update_curr(cfs_rq);

se can have been modified by find_matching_se(&se, &pse)

>         if (wakeup_preempt_entity(se, pse) == 1) {
>                 /*
>                  * Bias pick_next to pick the sched entity that is
> --
> 2.31.1
>