linux-kernel - Re: [PATCH] cfs: remove unused 'if' condition checking

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Date:	Fri, 16 Sep 2011 00:39:02 -0700
From:	Paul Turner <pjt@...gle.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cfs: remove unused 'if' condition checking

On 09/16/11 10:35, Wang Xingchao wrote:

Please include a one-line summary such as:
sched: remove extra nr_running check in check_preempt_tick

> nr_running must be more than 1, so remove the checking
>

Sure, reasonable.

Please expand this comment though, e.g.
We already test for nr_running > 1 within entity_tick so there is no 
need to recheck it within check_preempt_tick().

> Signed-off-by: Wang Xingchao<xingchao.wang@...el.com>

Reviewed-by: Paul Turner <pjt@...gle.com>

> ---
>   kernel/sched_fair.c |   16 ++++++++--------
>   1 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index 1ca2cd4..fef0bfd 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -1106,6 +1106,8 @@ static void
>   check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
>   {
>   	unsigned long ideal_runtime, delta_exec;
> +	struct sched_entity *se;
> +	s64 delta;
>
>   	ideal_runtime = sched_slice(cfs_rq, curr);
>   	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
> @@ -1127,16 +1129,14 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
>   	if (delta_exec<  sysctl_sched_min_granularity)

You've mangled the white space on the less-than.

>   		return;
>
> -	if (cfs_rq->nr_running>  1) {
> -		struct sched_entity *se = __pick_first_entity(cfs_rq);
> -		s64 delta = curr->vruntime - se->vruntime;
> +	se = __pick_first_entity(cfs_rq);
> +	delta = curr->vruntime - se->vruntime;
>
> -		if (delta<  0)
> -			return;
> +	if (delta<  0)

And here.

> +		return;
>
> -		if (delta>  ideal_runtime)
> -			resched_task(rq_of(cfs_rq)->curr);
> -	}
> +	if (delta>  ideal_runtime)

Here too.

> +		resched_task(rq_of(cfs_rq)->curr);
>   }
>
>   static void


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