linux-kernel - Re: [PATCH 2/6] zsmalloc: remove unnecessary alignment

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Date:	Wed, 25 Apr 2012 08:53:42 -0400
From:	Nitin Gupta <ngupta@...are.org>
To:	Minchan Kim <minchan@...nel.org>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/6] zsmalloc: remove unnecessary alignment

On 04/25/2012 02:23 AM, Minchan Kim wrote:

> It isn't necessary to align pool size with PAGE_SIZE.
> If I missed something, please let me know it.
> 
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>  drivers/staging/zsmalloc/zsmalloc-main.c |    5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
> index 504b6c2..b99ad9e 100644
> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
> @@ -489,14 +489,13 @@ fail:
>  
>  struct zs_pool *zs_create_pool(const char *name, gfp_t flags)
>  {
> -	int i, error, ovhd_size;
> +	int i, error;
>  	struct zs_pool *pool;
>  
>  	if (!name)
>  		return NULL;
>  
> -	ovhd_size = roundup(sizeof(*pool), PAGE_SIZE);
> -	pool = kzalloc(ovhd_size, GFP_KERNEL);
> +	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
>  	if (!pool)
>  		return NULL;
>  


pool metadata is rounded-up to avoid potential false-sharing problem
(though we could just roundup to cache_line_size()).

Thanks,
Nitin
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