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Subject[PATCH 02/12] Allow CONFIG_MIGRATION to be set without CONFIG_NUMA or memory hot-remove
Date
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>
---
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.
+
+#
# 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


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