linux-kernel - Re: [PATCH 3/6] change alloc function in alloc_slab

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Date:	Wed, 14 Apr 2010 08:40:16 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Bob Liu <lliubbo@...il.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 3/6] change alloc function in alloc_slab_page

On Wed, Apr 14, 2010 at 6:37 AM, David Rientjes <rientjes@...gle.com> wrote:
> On Wed, 14 Apr 2010, Minchan Kim wrote:
>
>> alloc_slab_page never calls alloc_pages_node with -1.
>> It means node's validity check is unnecessary.
>> So we can use alloc_pages_exact_node instead of alloc_pages_node.
>> It could avoid comparison and branch as 6484eb3e2a81807722 tried.
>>
>> Cc: Christoph Lameter <cl@...ux-foundation.org>
>> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
>> ---
>>  mm/slub.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/slub.c b/mm/slub.c
>> index b364844..9984165 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -1084,7 +1084,7 @@ static inline struct page *alloc_slab_page(gfp_t flags, int node,
>>       if (node == -1)
>>               return alloc_pages(flags, order);
>>       else
>> -             return alloc_pages_node(node, flags, order);
>> +             return alloc_pages_exact_node(node, flags, order);
>>  }
>>
>>  static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
>
> Slub changes need to go through its maintainer, Pekka Enberg
> <penberg@...helsinki.fi>.

Thanks, David. It was by mistake.

Pekka.

This changlog is bad.
I will change it with following as when I send v2.

"alloc_slab_page always checks nid == -1, so alloc_page_node can't be
called with -1.
 It means node's validity check in alloc_pages_node is unnecessary.
 So we can use alloc_pages_exact_node instead of alloc_pages_node.
 It could avoid comparison and branch as 6484eb3e2a81807722 tried."

Thanks.


-- 
Kind regards,
Minchan Kim
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