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authorRik van Riel <riel@redhat.com>2011-10-31 17:09:31 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-10-31 17:30:50 -0700
commite0887c19b2daa140f20ca8104bdc5740f39dbb86 (patch)
tree86330414eb04b5989e68661c205aa52d46ca7ebf /mm
parent21ee9f398be209ccbb62929d35961ca1ed48eec3 (diff)
downloadlinux-linaro-stable-e0887c19b2daa140f20ca8104bdc5740f39dbb86.tar.gz
vmscan: limit direct reclaim for higher order allocations
When suffering from memory fragmentation due to unfreeable pages, THP page faults will repeatedly try to compact memory. Due to the unfreeable pages, compaction fails. Needless to say, at that point page reclaim also fails to create free contiguous 2MB areas. However, that doesn't stop the current code from trying, over and over again, and freeing a minimum of 4MB (2UL << sc->order pages) at every single invocation. This resulted in my 12GB system having 2-3GB free memory, a corresponding amount of used swap and very sluggish response times. This can be avoided by having the direct reclaim code not reclaim from zones that already have plenty of free memory available for compaction. If compaction still fails due to unmovable memory, doing additional reclaim will only hurt the system, not help. [jweiner@redhat.com: change comment to explain the order check] Signed-off-by: Rik van Riel <riel@redhat.com> Acked-by: Johannes Weiner <jweiner@redhat.com> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Johannes Weiner <jweiner@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/vmscan.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index f51a33e8ed89..7e0f05797388 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2125,6 +2125,22 @@ static void shrink_zones(int priority, struct zonelist *zonelist,
continue;
if (zone->all_unreclaimable && priority != DEF_PRIORITY)
continue; /* Let kswapd poll it */
+ if (COMPACTION_BUILD) {
+ /*
+ * If we already have plenty of memory
+ * free for compaction, don't free any
+ * more. Even though compaction is
+ * invoked for any non-zero order,
+ * only frequent costly order
+ * reclamation is disruptive enough to
+ * become a noticable problem, like
+ * transparent huge page allocations.
+ */
+ if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&
+ (compaction_suitable(zone, sc->order) ||
+ compaction_deferred(zone)))
+ continue;
+ }
/*
* This steals pages from memory cgroups over softlimit
* and returns the number of reclaimed pages and