linux-kernel - Re: [PATCH] sched/fair: cleanup, clamp values with macros clamp() and max().

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Date:	Fri, 16 May 2014 12:20:05 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/fair: cleanup, clamp values with macros clamp()
 and max().

On Fri, May 16, 2014 at 12:12:34PM +0900, Dongsheng Yang wrote:
> Rather than use "if" to check and clamp values to allowed minmum or maxmum,
> this patch use macros clamp() and max() to clean it up.
> 
> Signed-off-by: Dongsheng Yang <yangds.fnst@...fujitsu.com>
> ---
>  kernel/sched/fair.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 7570dd9..939a7ab 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2041,10 +2041,7 @@ static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
>  	if (tg_weight)
>  		shares /= tg_weight;
>  
> -	if (shares < MIN_SHARES)
> -		shares = MIN_SHARES;
> -	if (shares > tg->shares)
> -		shares = tg->shares;
> +	shares = clamp(shares, MIN_SHARES, tg->shares);
>  
>  	return shares;
>  }
> @@ -4133,8 +4130,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
>  		 * those are clipped to [MIN_SHARES, ...) do so now. See
>  		 * calc_cfs_shares().
>  		 */
> -		if (wl < MIN_SHARES)
> -			wl = MIN_SHARES;
> +		wl = max(wl, MIN_SHARES);
>  
>  		/*
>  		 * wl = dw_i = S * (s'_i - s_i); see (3)

kernel/sched/fair.c: In function ‘calc_cfs_shares’:
kernel/sched/fair.c:2068:11: warning: comparison of distinct pointer types lacks a cast [enabled by default]
kernel/sched/fair.c:2068:11: warning: comparison of distinct pointer types lacks a cast [enabled by default]
kernel/sched/fair.c: In function ‘effective_load’:
kernel/sched/fair.c:4157:8: warning: comparison of distinct pointer types lacks a cast [enabled by default]
kernel/sched/fair.c: In function ‘migrate_task_rq_fair’:

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