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authorRik van Riel <riel@redhat.com>2011-10-31 17:09:31 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-08-01 12:27:15 -0700
commit4d4724067d512e7f17010112da8ec64917c192e7 (patch)
tree3d6bbaf757a38d6e1e52cc656590c1b33e63ce95 /mm
parent7554e3446a916363447a81a29f9300d3f2fbf503 (diff)
vmscan: limit direct reclaim for higher order allocations
commit e0887c19b2daa140f20ca8104bdc5740f39dbb86 upstream. Stable note: Not tracked on Bugzilla. THP and compaction was found to aggressively reclaim pages and stall systems under different situations that was addressed piecemeal over time. Paragraph 3 of this changelog is the motivation for this patch. 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> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 d375de3111ba..e1ae88b0b44e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2059,6 +2059,22 @@ 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