Dont allocate pagesets for unpopulated zones.

We do not need to allocate pagesets for unpopulated zones.
This saves 1 mio pagesets per unpopulated zone on a 1k cpu / 1k node box.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.18-rc7-mm1/mm/page_alloc.c
===================================================================
--- linux-2.6.18-rc7-mm1.orig/mm/page_alloc.c	2006-09-19 09:27:03.624466971 -0500
+++ linux-2.6.18-rc7-mm1/mm/page_alloc.c	2006-09-19 09:38:33.058767522 -0500
@@ -1908,6 +1908,9 @@ static int __cpuinit process_zones(int c
 		if (!populated_zone(zone))
 			continue;
 
+		if (!populated_zone(zone))
+			continue;
+
 		zone_pcp(zone, cpu) = kmalloc_node(sizeof(struct per_cpu_pageset),
 					 GFP_KERNEL, cpu_to_node(cpu));
 		if (!zone_pcp(zone, cpu))