mm: use two zonelist that are filtered by GFP mask

Currently a node has two sets of zonelists, one for each zone type in the
system and a second set for GFP_THISNODE allocations.  Based on the zones
allowed by a gfp mask, one of these zonelists is selected.  All of these
zonelists consume memory and occupy cache lines.

This patch replaces the multiple zonelists per-node with two zonelists.  The
first contains all populated zones in the system, ordered by distance, for
fallback allocations when the target/preferred node has no free pages.  The
second contains all populated zones in the node suitable for GFP_THISNODE
allocations.

An iterator macro is introduced called for_each_zone_zonelist() that interates
through each zone allowed by the GFP flags in the selected zonelist.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/mm/slab.c b/mm/slab.c
index 5488c54..2985184 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3243,6 +3243,8 @@ static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags)
 	struct zonelist *zonelist;
 	gfp_t local_flags;
 	struct zone **z;
+	struct zone *zone;
+	enum zone_type high_zoneidx = gfp_zone(flags);
 	void *obj = NULL;
 	int nid;
 
@@ -3257,10 +3259,10 @@ retry:
 	 * Look through allowed nodes for objects available
 	 * from existing per node queues.
 	 */
-	for (z = zonelist->zones; *z && !obj; z++) {
-		nid = zone_to_nid(*z);
+	for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
+		nid = zone_to_nid(zone);
 
-		if (cpuset_zone_allowed_hardwall(*z, flags) &&
+		if (cpuset_zone_allowed_hardwall(zone, flags) &&
 			cache->nodelists[nid] &&
 			cache->nodelists[nid]->free_objects)
 				obj = ____cache_alloc_node(cache,