linux-kernel - Re: [PATCH 3/7] Allow CONFIG_MIGRATION to be set without CONFIG

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Message-ID: <Pine.LNX.4.64.0705291948100.5669@skynet.skynet.ie>
Date:	Tue, 29 May 2007 19:49:01 +0100 (IST)
From:	Mel Gorman <mel@....ul.ie>
To:	Christoph Lameter <clameter@....com>
cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	kamezawa.hiroyu@...fujitsu.com
Subject: Re: [PATCH 3/7] Allow CONFIG_MIGRATION to be set without CONFIG_NUMA

On Tue, 29 May 2007, Christoph Lameter wrote:

> On Tue, 29 May 2007, Mel Gorman wrote:
>
>>>> +config SYSCALL_MOVE_PAGES
>>>> +	def_bool y
>>>> +	depends on MIGRATION && NUMA
>>>> +
>>>
>>> Do we really need the CONFIG_SYSCALL_MOVE_PAGES? I think you will directly
>>> access the lower levels. So why have it? CONFIG_SYSCALL_MOVE_PAGES ==
>>> CONFIG_NUMA.
>>
>> Without SYSCALL_MOVE_PAGES, the check in migrate.h becomes
>>
>> #if defined(CONFIG_NUMA) && defined(CONFIG_MIGRATION)
>> /* Check if a vma is migratable */
>> static inline int vma_migratable(struct vm_area_struct *vma)
>> #endif
>
> Why do you need vma_migratable for the CONFIG_MIGRATION case? The use of
> vma_migratable in a !NUMA sitation would not be working right as far as I
> can tell.
>
> #ifdef CONFIG_NUMA
>
> is fine.
>

Makes sense.

>> That in itself is fine but in mm/migrate.c I didn't want to define
>> sys_move_pages() in the non-NUMA case. Whatever about the header file where
>> SYSCALL_MOVE_PAGES obscures understanding, I think it makes sense to have
>> SYSCALL_MOVE_PAGES for mm/migrate.c . What do you think?
>
> Why do you need sys_move_pages for the non-NUMA case?
>
> The low level function that I intended to be used by defrag is
> migrate_pages and that one is outside of #ifdef CONFIG_NUMA.
>

Also make sense. It'll be fixed up in the next verion minus the 
SYSCALL_MOVE_PAGES dirt. It'll even simplify the patch.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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