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mm: prepare to remove /proc/sys/vm/hugepages_treat_as_movable

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Now hugepage migration is enabled, although restricted on pmd-based
hugepages for now (due to lack of testing.) So we should allocate
migratable hugepages from ZONE_MOVABLE if possible.

This patch makes GFP flags in hugepage allocation dependent on migration
support, not only the value of hugepages_treat_as_movable.  It provides no
change on the behavior for architectures which do not support hugepage
migration,

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Rik van Riel <riel@redhat.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Naoya Horiguchi
2013-09-11 14:22:13 -07:00
committed by Linus Torvalds
parent 83467efbdb
commit 86cdb465cf
3 changed files with 33 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Documentation/sysctl/vm.txt
+18 -10
View File
@@ -200,17 +200,25 @@ fragmentation index is <= extfrag_threshold. The default value is 500.
hugepages_treat_as_movable
This parameter is only useful when kernelcore= is specified at boot time to
create ZONE_MOVABLE for pages that may be reclaimed or migrated. Huge pages
are not movable so are not normally allocated from ZONE_MOVABLE. A non-zero
value written to hugepages_treat_as_movable allows huge pages to be allocated
from ZONE_MOVABLE.
This parameter controls whether we can allocate hugepages from ZONE_MOVABLE
or not. If set to non-zero, hugepages can be allocated from ZONE_MOVABLE.
ZONE_MOVABLE is created when kernel boot parameter kernelcore= is specified,
so this parameter has no effect if used without kernelcore=.
Once enabled, the ZONE_MOVABLE is treated as an area of memory the huge
pages pool can easily grow or shrink within. Assuming that applications are
not running that mlock() a lot of memory, it is likely the huge pages pool
can grow to the size of ZONE_MOVABLE by repeatedly entering the desired value
into nr_hugepages and triggering page reclaim.
Hugepage migration is now available in some situations which depend on the
architecture and/or the hugepage size. If a hugepage supports migration,
allocation from ZONE_MOVABLE is always enabled for the hugepage regardless
of the value of this parameter.
IOW, this parameter affects only non-migratable hugepages.
Assuming that hugepages are not migratable in your system, one usecase of
this parameter is that users can make hugepage pool more extensible by
enabling the allocation from ZONE_MOVABLE. This is because on ZONE_MOVABLE
page reclaim/migration/compaction work more and you can get contiguous
memory more likely. Note that using ZONE_MOVABLE for non-migratable
hugepages can do harm to other features like memory hotremove (because
memory hotremove expects that memory blocks on ZONE_MOVABLE are always
removable,) so it's a trade-off responsible for the users.
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