[PATCH] mm: do not check unpopulated zones for draining and counter updates

If a zone is unpopulated then we do not need to check for pages that are to
be drained and also not for vm counters that may need to be updated.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/page_alloc.c

@@ -633,7 +633,7 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
 #ifdef CONFIG_NUMA
 /*
  * Called from the slab reaper to drain pagesets on a particular node that
- * belong to the currently executing processor.
+ * belongs to the currently executing processor.
  * Note that this function must be called with the thread pinned to
  * a single processor.
  */
@@ -647,6 +647,9 @@ void drain_node_pages(int nodeid)
 		struct zone *zone = NODE_DATA(nodeid)->node_zones + z;
 		struct per_cpu_pageset *pset;
 
+		if (!populated_zone(zone))
+			continue;
+
 		pset = zone_pcp(zone, smp_processor_id());
 		for (i = 0; i < ARRAY_SIZE(pset->pcp); i++) {
 			struct per_cpu_pages *pcp;

mm/vmstat.c

@@ -321,6 +321,9 @@ void refresh_cpu_vm_stats(int cpu)
 	for_each_zone(zone) {
 		struct per_cpu_pageset *pcp;
 
+		if (!populated_zone(zone))
+			continue;
+
 		pcp = zone_pcp(zone, cpu);
 
 		for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)