linux-kernel - Re: [PATCH] mm: percpu: micro-optimize round-to-even

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Message-ID: <20140619132536.GF11042@htj.dyndns.org>
Date:	Thu, 19 Jun 2014 09:25:36 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Christoph Lameter <cl@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: percpu: micro-optimize round-to-even

On Thu, Jun 19, 2014 at 12:02:29PM +0200, Rasmus Villemoes wrote:
> This change shaves a few bytes off the generated code.
> 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
>  mm/percpu.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 2ddf9a9..978097f 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -720,8 +720,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved)
>  	if (unlikely(align < 2))
>  		align = 2;
>  
> -	if (unlikely(size & 1))
> -		size++;
> +	size += size & 1;

I'm not gonna apply this.  This isn't that hot a path.  It's not
worthwhile to micro optimize code like this.

Thanks.

-- 
tejun
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