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    SubjectRe: [PATCH 05/12] Allow CONFIG_MIGRATION to be set without CONFIG_NUMA or memory hot-remove
    On Fri, Feb 19, 2010 at 09:21:11AM +0900, KAMEZAWA Hiroyuki wrote:
    > On Thu, 18 Feb 2010 18:02:35 +0000
    > Mel Gorman <mel@csn.ul.ie> wrote:
    >
    > > CONFIG_MIGRATION currently depends on CONFIG_NUMA or on the architecture
    > > being able to hot-remove memory. The main users of page migration such as
    > > sys_move_pages(), sys_migrate_pages() and cpuset process migration are
    > > only beneficial on NUMA so it makes sense.
    > >
    > > 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.
    > >
    > > Signed-off-by: Mel Gorman <mel@csn.ul.ie>
    > > Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
    > > Reviewed-by: Rik van Riel <riel@redhat.com>
    >
    > Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > But see below.
    >
    > > ---
    > > mm/Kconfig | 20 ++++++++++++++++----
    > > 1 files changed, 16 insertions(+), 4 deletions(-)
    > >
    > > diff --git a/mm/Kconfig b/mm/Kconfig
    > > index 17b8947..b1c2781 100644
    > > --- a/mm/Kconfig
    > > +++ b/mm/Kconfig
    > > @@ -168,17 +168,29 @@ config SPLIT_PTLOCK_CPUS
    > > default "4"
    > >
    > > #
    > > +# support for memory compaction
    > > +config COMPACTION
    > > + bool "Allow for memory compaction"
    > > + def_bool y
    > > + select MIGRATION
    > > + depends on EXPERIMENTAL && HUGETLBFS
    > > + help
    > > + Allows the compaction of memory for the allocation of huge pages.
    > > +
    >
    > I think
    > + depends on MMU
    >

    Agreed. Thanks

    > > +#
    > > # support for page migration
    > > #
    > > config MIGRATION
    > > bool "Page migration"
    > > def_bool y
    > > - depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
    > > + depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
    > > help
    > > Allows the migration of the physical location of pages of processes
    > > - while the virtual addresses are not changed. This is useful for
    > > - example on NUMA systems to put pages nearer to the processors accessing
    > > - the page.
    > > + while the virtual addresses are not changed. This is useful in
    > > + two situations. The first is on NUMA systems to put pages nearer
    > > + to the processors accessing. The second is when allocating huge
    > > + pages as migration can relocate pages to satisfy a huge page
    > > + allocation instead of reclaiming.
    > >
    > > config PHYS_ADDR_T_64BIT
    > > def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
    > > --
    > > 1.6.5
    > >
    > > --
    > > To unsubscribe, send a message with 'unsubscribe linux-mm' in
    > > the body to majordomo@kvack.org. For more info on Linux MM,
    > > see: http://www.linux-mm.org/ .
    > > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
    > >
    >

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


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