Re: [PATCH 1/7] Allow CONFIG_MIGRATION to be set withoutCONFIG_NUMA

From: Mel Gorman
Date: Tue Jan 19 2010 - 08:01:15 EST

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

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