3 files changed, 56 insertions, 14 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 57700038e669..7d7e4fe0fda8 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -33,9 +33,15 @@
  */
 #define PAGE_ALLOC_COSTLY_ORDER 3
 
+#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY
 #define MIGRATE_UNMOVABLE     0
 #define MIGRATE_MOVABLE       1
 #define MIGRATE_TYPES         2
+#else
+#define MIGRATE_UNMOVABLE     0
+#define MIGRATE_MOVABLE       0
+#define MIGRATE_TYPES         1
+#endif
 
 #define for_each_migratetype_order(order, type) \
         for (order = 0; order < MAX_ORDER; order++) \
diff --git a/init/Kconfig b/init/Kconfig
index 54f31a191b88..bab643f7717f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -607,6 +607,19 @@ config BASE_SMALL
         default 0 if BASE_FULL
         default 1 if !BASE_FULL
 
+config PAGE_GROUP_BY_MOBILITY
+        bool "Group pages based on their mobility in the page allocator"
+        def_bool y
+        help
+          The standard allocator will fragment memory over time which means
+          that high order allocations will fail even if kswapd is running. If
+          this option is set, the allocator will try and group page types
+          based on their ability to migrate or reclaim. This is a best effort
+          attempt at lowering fragmentation which a few workloads care about.
+          The loss is a more complex allocator that may perform slower. If
+          you are interested in working with large pages, say Y and set
+          /proc/sys/vm/min_free_bytes to 16374. Otherwise say N
+
 menuconfig MODULES
         bool "Enable loadable module support"
         help
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e3e726bd2858..fea1e3b56c3d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -158,6 +158,7 @@ int nr_node_ids __read_mostly = MAX_NUMNODES;
 EXPORT_SYMBOL(nr_node_ids);
 #endif
 
+#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY
 static inline int get_pageblock_migratetype(struct page *page)
 {
         return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);
@@ -174,6 +175,22 @@ static inline int gfpflags_to_migratetype(gfp_t gfp_flags)
         return ((gfp_flags & __GFP_MOVABLE) != 0);
 }
 
+#else
+static inline int get_pageblock_migratetype(struct page *page)
+{
+        return MIGRATE_UNMOVABLE;
+}
+
+static void set_pageblock_migratetype(struct page *page, int migratetype)
+{
+}
+
+static inline int gfpflags_to_migratetype(gfp_t gfp_flags)
+{
+        return MIGRATE_UNMOVABLE;
+}
+#endif /* CONFIG_PAGE_GROUP_BY_MOBILITY */
+
 #ifdef CONFIG_DEBUG_VM
 static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
 {
@@ -653,6 +670,7 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
         return 0;
 }
 
+#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY
 /*
  * This array describes the order lists are fallen back to when
  * the free lists for the desirable migrate type are depleted
@@ -709,6 +727,13 @@ static struct page *__rmqueue_fallback(struct zone *zone, int order,
 
         return NULL;
 }
+#else
+static struct page *__rmqueue_fallback(struct zone *zone, int order,
+                                                int start_migratetype)
+{
+        return NULL;
+}
+#endif /* CONFIG_PAGE_GROUP_BY_MOBILITY */
 
 /* 
  * Do the hard work of removing an element from the buddy allocator.
@@ -953,27 +978,25 @@ again:
                         if (unlikely(!pcp->count))
                                 goto failed;
                 }
+
+#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY
                 /* Find a page of the appropriate migrate type */
-                list_for_each_entry(page, &pcp->list, lru) {
-                        if (page_private(page) == migratetype) {
-                                list_del(&page->lru);
-                                pcp->count--;
+                list_for_each_entry(page, &pcp->list, lru)
+                        if (page_private(page) == migratetype)
                                 break;
-                        }
-                }
 
-                /*
-                 * Check if a page of the appropriate migrate type
-                 * was found. If not, allocate more to the pcp list
-                 */
-                if (&page->lru == &pcp->list) {
+                /* Allocate more to the pcp list if necessary */
+                if (unlikely(&page->lru == &pcp->list)) {
                         pcp->count += rmqueue_bulk(zone, 0,
                                         pcp->batch, &pcp->list, migratetype);
                         page = list_entry(pcp->list.next, struct page, lru);
-                        VM_BUG_ON(page_private(page) != migratetype);
-                        list_del(&page->lru);
-                        pcp->count--;
                 }
+#else
+                page = list_entry(pcp->list.next, struct page, lru);
+#endif /* CONFIG_PAGE_GROUP_BY_MOBILITY */
+
+                list_del(&page->lru);
+                pcp->count--;
         } else {
                 spin_lock_irqsave(&zone->lock, flags);
                 page = __rmqueue(zone, order, migratetype);