Add auto zone ordering configuration.
This function will select ZONE_ORDER_NODE when
There are only ZONE_DMA or ZONE_DMA32.
|| size of (ZONE_DMA/DMA32) > (System Total Memory)/2
|| Assume Node(A)
Node (A) is enough big &&
Node (A)'s ZONE_DMA/DMA32 occupies 60% of Node(A)'s memory.
(In this case, ZONE_ORDER_ZONE may not offer enough locality...)
otherwise, ZONE_ORDER_ZONE is selected.
Maybe there is no best way to configure zone order. I wrote this base on
my experience and discussion on the list.
Anyway, a user can specifiy zone order from boot option/sysctl.
Signed-Off-By: KAMEZAWA Hiroyuki <[email protected]>
mm/page_alloc.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 49 insertions(+), 2 deletions(-)
Index: linux-2.6.21-mm2/mm/page_alloc.c
===================================================================
--- linux-2.6.21-mm2.orig/mm/page_alloc.c
+++ linux-2.6.21-mm2/mm/page_alloc.c
@@ -2204,8 +2204,55 @@ static void build_zonelists_in_zone_orde
static int default_zonelist_order(void)
{
- /* dummy, just select node order. */
- return ZONELIST_ORDER_NODE;
+ 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 sytem.
+ * If they are really small and used heavily, the system can fall
+ * into OOM very easily.
+ * This function detect ZONE_DMA/DMA32 size and confgigures 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->present_pages;
+ total_size += z->present_pages;
+ }
+ }
+ }
+ 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 / (num_online_nodes() + 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;
}
static void set_zonelist_order(void)
-
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