linux-kernel - Re: [PATCH] sched: core: Optimize the structure of 'tg_cfs_schedulable

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Message-ID: <xm26o7onvy2j.fsf@google.com>
Date:   Mon, 20 Mar 2023 15:48:36 -0700
From:   Benjamin Segall <bsegall@...gle.com>
To:     Li kunyu <kunyu@...china.com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, mgorman@...e.de, bristot@...hat.com,
        vschneid@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: core: Optimize the structure of
 'tg_cfs_schedulable_down' function

Li kunyu <kunyu@...china.com> writes:

> Optimize if branches and define  in the branch statement
> block　parent_quota variable.

It's not an optimization; it is arguably a slight style improvement.

>
> Signed-off-by: Li kunyu <kunyu@...china.com>
> ---
>  kernel/sched/core.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 488655f2319f..7e8535d2e36d 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -10915,15 +10915,12 @@ static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
>  {
>  	struct cfs_schedulable_data *d = data;
>  	struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
> -	s64 quota = 0, parent_quota = -1;
> +	s64 quota = RUNTIME_INF;
>  
> -	if (!tg->parent) {
> -		quota = RUNTIME_INF;
> -	} else {
> +	if (tg->parent) {
>  		struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
> -
> +		s64 parent_quota = parent_b->hierarchical_quota;
>  		quota = normalize_cfs_quota(tg, d);
> -		parent_quota = parent_b->hierarchical_quota;
>  
>  		/*
>  		 * Ensure max(child_quota) <= parent_quota.  On cgroup2,