1 files changed, 20 insertions, 58 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index eac31a6059c0..bfb73e025e02 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3614,68 +3614,30 @@ static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes)
 	zonelist->_zonerefs[pos].zone_idx = 0;
 }
 
+#if defined(CONFIG_64BIT)
+/*
+ * Devices that require DMA32/DMA are relatively rare and do not justify a
+ * penalty to every machine in case the specialised case applies. Default
+ * to Node-ordering on 64-bit NUMA machines
+ */
+static int default_zonelist_order(void)
+{
+	return ZONELIST_ORDER_NODE;
+}
+#else
+/*
+ * On 32-bit, the Normal zone needs to be preserved for allocations accessible
+ * by the kernel. If processes running on node 0 deplete the low memory zone
+ * then reclaim will occur more frequency increasing stalls and potentially
+ * be easier to OOM if a large percentage of the zone is under writeback or
+ * dirty. The problem is significantly worse if CONFIG_HIGHPTE is not set.
+ * Hence, default to zone ordering on 32-bit.
+ */
 static int default_zonelist_order(void)
 {
-	int nid, zone_type;
-	unsigned long low_kmem_size, total_size;
-	struct zone *z;
-	int average_size;
-	/*
-	 * ZONE_DMA and ZONE_DMA32 can be very small area in the system.
-	 * If they are really small and used heavily, the system can fall
-	 * into OOM very easily.
-	 * This function detect ZONE_DMA/DMA32 size and configures zone order.
-	 */
-	/* Is there ZONE_NORMAL ? (ex. ppc has only DMA zone..) */
-	low_kmem_size = 0;
-	total_size = 0;
-	for_each_online_node(nid) {
-		for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
-			z = &NODE_DATA(nid)->node_zones[zone_type];
-			if (populated_zone(z)) {
-				if (zone_type < ZONE_NORMAL)
-					low_kmem_size += z->managed_pages;
-				total_size += z->managed_pages;
-			} else if (zone_type == ZONE_NORMAL) {
-				/*
-				 * If any node has only lowmem, then node order
-				 * is preferred to allow kernel allocations
-				 * locally; otherwise, they can easily infringe
-				 * on other nodes when there is an abundance of
-				 * lowmem available to allocate from.
-				 */
-				return ZONELIST_ORDER_NODE;
-			}
-		}
-	}
-	if (!low_kmem_size ||  /* there are no DMA area. */
-	    low_kmem_size > total_size/2) /* DMA/DMA32 is big. */
-		return ZONELIST_ORDER_NODE;
-	/*
-	 * look into each node's config.
-	 * If there is a node whose DMA/DMA32 memory is very big area on
-	 * local memory, NODE_ORDER may be suitable.
-	 */
-	average_size = total_size /
-				(nodes_weight(node_states[N_MEMORY]) + 1);
-	for_each_online_node(nid) {
-		low_kmem_size = 0;
-		total_size = 0;
-		for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
-			z = &NODE_DATA(nid)->node_zones[zone_type];
-			if (populated_zone(z)) {
-				if (zone_type < ZONE_NORMAL)
-					low_kmem_size += z->present_pages;
-				total_size += z->present_pages;
-			}
-		}
-		if (low_kmem_size &&
-		    total_size > average_size && /* ignore small node */
-		    low_kmem_size > total_size * 70/100)
-			return ZONELIST_ORDER_NODE;
-	}
 	return ZONELIST_ORDER_ZONE;
 }
+#endif /* CONFIG_64BIT */
 
 static void set_zonelist_order(void)
 {