path: root/mm
diff options
authorMel Gorman <mgorman@suse.de>2013-04-29 15:07:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-29 15:54:35 -0700
commitfed2719e7a8612471bd17113ed326d38df434f17 (patch)
tree7c3c477ad75e885b68ccfcc473bffd6f9b9dcbea /mm
parent8e2cdbcb86b0abefc3d07922c48edb01fece3c56 (diff)
mm: page_alloc: avoid marking zones full prematurely after zone_reclaim()
The following problem was reported against a distribution kernel when zone_reclaim was enabled but the same problem applies to the mainline kernel. The reproduction case was as follows 1. Run numactl -m +0 dd if=largefile of=/dev/null This allocates a large number of clean pages in node 0 2. numactl -N +0 memhog 0.5*Mg This start a memory-using application in node 0. The expected behaviour is that the clean pages get reclaimed and the application uses node 0 for its memory. The observed behaviour was that the memory for the memhog application was allocated off-node since commits cd38b115d5ad ("mm: page allocator: initialise ZLC for first zone eligible for zone_reclaim") and commit 76d3fbf8fbf6 ("mm: page allocator: reconsider zones for allocation after direct reclaim"). The assumption of those patches was that it was always preferable to allocate quickly than stall for long periods of time and they were meant to take care that the zone was only marked full when necessary but an important case was missed. In the allocator fast path, only the low watermarks are checked. If the zones free pages are between the low and min watermark then allocations from the allocators slow path will succeed. However, zone_reclaim will only reclaim SWAP_CLUSTER_MAX or 1<<order pages. There is no guarantee that this will meet the low watermark causing the zone to be marked full prematurely. This patch will only mark the zone full after zone_reclaim if it the min watermarks are checked or if page reclaim failed to make sufficient progress. [mhocko@suse.cz: fix alloc_flags test] Signed-off-by: Mel Gorman <mgorman@suse.de> Reported-by: Hedi Berriche <hedi@sgi.com> Tested-by: Hedi Berriche <hedi@sgi.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Signed-off-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files changed, 16 insertions, 1 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7350986bbf9..b54c5cbf020 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1942,9 +1942,24 @@ zonelist_scan:
/* did we reclaim enough */
- if (!zone_watermark_ok(zone, order, mark,
+ if (zone_watermark_ok(zone, order, mark,
classzone_idx, alloc_flags))
+ goto try_this_zone;
+ /*
+ * Failed to reclaim enough to meet watermark.
+ * Only mark the zone full if checking the min
+ * watermark or if we failed to reclaim just
+ * 1<<order pages or else the page allocator
+ * fastpath will prematurely mark zones full
+ * when the watermark is between the low and
+ * min watermarks.
+ */
+ if (((alloc_flags & ALLOC_WMARK_MASK) == ALLOC_WMARK_MIN) ||
goto this_zone_full;
+ continue;