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

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Date:	Fri, 16 Sep 2011 13:54:15 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Wang Xingchao <xingchao.wang@...el.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, peterz@...radead.org
Subject: Re: [PATCH] cfs: remove unused 'if' condition checking

On Fri, Sep 16, 2011 at 01:35:52PM -0400, Wang Xingchao wrote:
> nr_running must be more than 1, so remove the checking
> 
> Signed-off-by: Wang Xingchao <xingchao.wang@...el.com>

The patch looks good. And comments below.

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

It's better to add some comments to explain why se could not be NULL.

Thanks,
Yong

> +	se = __pick_first_entity(cfs_rq);
> +	delta = curr->vruntime - se->vruntime;
>  
> -		if (delta < 0)
> -			return;
> +	if (delta < 0)
> +		return;
>  
> -		if (delta > ideal_runtime)
> -			resched_task(rq_of(cfs_rq)->curr);
> -	}
> +	if (delta > ideal_runtime)
> +		resched_task(rq_of(cfs_rq)->curr);
>  }
>  
>  static void
> -- 
> 1.7.1
> 
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