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From: Mel Gorman on 30 Mar 2010 05:20
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(a)csn.ul.ie>
Reviewed-by: Christoph Lameter <cl(a)linux-foundation.org>
Reviewed-by: Rik van Riel <riel(a)redhat.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com>
mm/Kconfig | 18 +++++++++++++++---
1 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/mm/Kconfig b/mm/Kconfig
index 9c61158..4fd75a0 100644
@@ -172,6 +172,16 @@ config SPLIT_PTLOCK_CPUS
+# support for memory compaction
+ bool "Allow for memory compaction"
+ def_bool y
+ select MIGRATION
+ depends on EXPERIMENTAL && HUGETLBFS && MMU
+ Allows the compaction of memory for the allocation of huge pages.
# support for page migration
@@ -180,9 +190,11 @@ config MIGRATION
depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
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.
def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
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