linux-kernel - Re: [PATCH 1/7] Allow CONFIG_MIGRATION to be set without CONFIG

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Message-ID: <20100119130055.GC23881@csn.ul.ie>
Date:	Tue, 19 Jan 2010 13:00:55 +0000
From:	Mel Gorman <mel@....ul.ie>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/7] Allow CONFIG_MIGRATION to be set without
	CONFIG_NUMA

On Thu, Jan 07, 2010 at 01:46:03PM -0800, David Rientjes wrote:
> On Wed, 6 Jan 2010, Mel Gorman wrote:
> 
> > CONFIG_MIGRATION currently depends on CONFIG_NUMA. The current users of
> > page migration such as sys_move_pages(), sys_migrate_pages() and cpuset
> > process migration are ordinarily only beneficial on NUMA.
> > 
> > As memory compaction will operate within a zone and is useful on both NUMA
> > and non-NUMA systems, this patch allows CONFIG_MIGRATION to be set if the
> > user selects CONFIG_COMPACTION as an option.
> > 
> > TODO
> >   o After this patch is applied, the migration core is available but it
> >     also makes NUMA-specific features available. This is too much
> >     exposure so revisit this.
> > 
> 
> CONFIG_MIGRATION is no longer strictly dependent on CONFIG_NUMA since 
> ARCH_ENABLE_MEMORY_HOTREMOVE has allowed it to be configured for UMA 
> machines.  All strictly NUMA features in the migration core should be 
> isolated under its #ifdef CONFIG_NUMA (sys_move_pages()) in mm/migrate.c 
> or by simply not compiling mm/mempolicy.c (sys_migrate_pages()), so this 
> patch looks fine as is (although the "help" text for CONFIG_MIGRATION 
> could be updated to reflect that it's useful for both memory hot-remove 
> and now compaction).
> 

That does appear to be the case, thanks. I had not double-checked
closely and it was somewhat of a problem when the series was first
developed.

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