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-rw-r--r--mm/page_alloc.c78
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)
{