From 5e9a900f3b9bdc89dcf585f7ac930079641c57f0 Mon Sep 17 00:00:00 2001
From: Mel Gorman <mel@csn.ul.ie>
Date: Mon, 24 May 2010 14:32:32 -0700
Subject: [PATCH] --- yaml --- r: 198251 b: refs/heads/master c:
 4f92e2586b43a2402e116055d4edda704f911b5b h: refs/heads/master i:   198249:
 efa15c8add374226e4a4492ed6ad75aa310aed7b   198247:
 8fe06cc75ab718cbc2fa511ad504e682a1d931ca v: v3

---
 [refs]                           |  2 +-
 trunk/include/linux/compaction.h | 39 ++++++++++++++++++++++++++++++++
 trunk/include/linux/mmzone.h     |  9 ++++++++
 trunk/mm/page_alloc.c            |  5 +++-
 4 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index 2c0f0529d614..ea370a06ee97 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 5e7719058079a1423ccce56148b0aaa56b2df821
+refs/heads/master: 4f92e2586b43a2402e116055d4edda704f911b5b
diff --git a/trunk/include/linux/compaction.h b/trunk/include/linux/compaction.h
index 3719325c6091..5ac51552d908 100644
--- a/trunk/include/linux/compaction.h
+++ b/trunk/include/linux/compaction.h
@@ -22,6 +22,36 @@ extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
 extern int fragmentation_index(struct zone *zone, unsigned int order);
 extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
 			int order, gfp_t gfp_mask, nodemask_t *mask);
+
+/* Do not skip compaction more than 64 times */
+#define COMPACT_MAX_DEFER_SHIFT 6
+
+/*
+ * Compaction is deferred when compaction fails to result in a page
+ * allocation success. 1 << compact_defer_limit compactions are skipped up
+ * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
+ */
+static inline void defer_compaction(struct zone *zone)
+{
+	zone->compact_considered = 0;
+	zone->compact_defer_shift++;
+
+	if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
+		zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
+}
+
+/* Returns true if compaction should be skipped this time */
+static inline bool compaction_deferred(struct zone *zone)
+{
+	unsigned long defer_limit = 1UL << zone->compact_defer_shift;
+
+	/* Avoid possible overflow */
+	if (++zone->compact_considered > defer_limit)
+		zone->compact_considered = defer_limit;
+
+	return zone->compact_considered < (1UL << zone->compact_defer_shift);
+}
+
 #else
 static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
 			int order, gfp_t gfp_mask, nodemask_t *nodemask)
@@ -29,6 +59,15 @@ static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
 	return COMPACT_CONTINUE;
 }
 
+static inline void defer_compaction(struct zone *zone)
+{
+}
+
+static inline bool compaction_deferred(struct zone *zone)
+{
+	return 1;
+}
+
 #endif /* CONFIG_COMPACTION */
 
 #if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
diff --git a/trunk/include/linux/mmzone.h b/trunk/include/linux/mmzone.h
index cf9e458e96b0..fd55f725a09e 100644
--- a/trunk/include/linux/mmzone.h
+++ b/trunk/include/linux/mmzone.h
@@ -321,6 +321,15 @@ struct zone {
 	unsigned long		*pageblock_flags;
 #endif /* CONFIG_SPARSEMEM */
 
+#ifdef CONFIG_COMPACTION
+	/*
+	 * On compaction failure, 1<<compact_defer_shift compactions
+	 * are skipped before trying again. The number attempted since
+	 * last failure is tracked with compact_considered.
+	 */
+	unsigned int		compact_considered;
+	unsigned int		compact_defer_shift;
+#endif
 
 	ZONE_PADDING(_pad1_)
 
diff --git a/trunk/mm/page_alloc.c b/trunk/mm/page_alloc.c
index cd88a860f088..95ad42de5a87 100644
--- a/trunk/mm/page_alloc.c
+++ b/trunk/mm/page_alloc.c
@@ -1769,7 +1769,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
 {
 	struct page *page;
 
-	if (!order)
+	if (!order || compaction_deferred(preferred_zone))
 		return NULL;
 
 	*did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask,
@@ -1785,6 +1785,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
 				alloc_flags, preferred_zone,
 				migratetype);
 		if (page) {
+			preferred_zone->compact_considered = 0;
+			preferred_zone->compact_defer_shift = 0;
 			count_vm_event(COMPACTSUCCESS);
 			return page;
 		}
@@ -1795,6 +1797,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
 		 * but not enough to satisfy watermarks.
 		 */
 		count_vm_event(COMPACTFAIL);
+		defer_compaction(preferred_zone);
 
 		cond_resched();
 	}