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| author | Mel Gorman <mel@csn.ul.ie> | 2009-06-16 15:33:22 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-16 19:47:45 -0700 |
| commit | fa5e084e43eb14c14942027e1e2e894aeed96097 (patch) | |
| tree | 3e7ebf714858e8dd1de7042fd1ef62294a3ec20f /mm/internal.h | |
| parent | 90afa5de6f3fa89a733861e843377302479fcf7e (diff) | |
| download | blackbird-op-linux-fa5e084e43eb14c14942027e1e2e894aeed96097.tar.gz blackbird-op-linux-fa5e084e43eb14c14942027e1e2e894aeed96097.zip | |
vmscan: do not unconditionally treat zones that fail zone_reclaim() as full
On NUMA machines, the administrator can configure zone_reclaim_mode that
is a more targetted form of direct reclaim. On machines with large NUMA
distances for example, a zone_reclaim_mode defaults to 1 meaning that
clean unmapped pages will be reclaimed if the zone watermarks are not
being met. The problem is that zone_reclaim() failing at all means the
zone gets marked full.
This can cause situations where a zone is usable, but is being skipped
because it has been considered full. Take a situation where a large tmpfs
mount is occuping a large percentage of memory overall. The pages do not
get cleaned or reclaimed by zone_reclaim(), but the zone gets marked full
and the zonelist cache considers them not worth trying in the future.
This patch makes zone_reclaim() return more fine-grained information about
what occured when zone_reclaim() failued. The zone only gets marked full
if it really is unreclaimable. If it's a case that the scan did not occur
or if enough pages were not reclaimed with the limited reclaim_mode, then
the zone is simply skipped.
There is a side-effect to this patch. Currently, if zone_reclaim()
successfully reclaimed SWAP_CLUSTER_MAX, an allocation attempt would go
ahead. With this patch applied, zone watermarks are rechecked after
zone_reclaim() does some work.
This bug was introduced by commit 9276b1bc96a132f4068fdee00983c532f43d3a26
("memory page_alloc zonelist caching speedup") way back in 2.6.19 when the
zonelist_cache was introduced. It was not intended that zone_reclaim()
aggressively consider the zone to be full when it failed as full direct
reclaim can still be an option. Due to the age of the bug, it should be
considered a -stable candidate.
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/internal.h')
| -rw-r--r-- | mm/internal.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/internal.h b/mm/internal.h index f02c7508068d..f290c4db528b 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -259,4 +259,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, int len, int flags, struct page **pages, struct vm_area_struct **vmas); +#define ZONE_RECLAIM_NOSCAN -2 +#define ZONE_RECLAIM_FULL -1 +#define ZONE_RECLAIM_SOME 0 +#define ZONE_RECLAIM_SUCCESS 1 #endif |
