[patch 01/10] Memoryless nodes: Fix GFP_THISNODE behavior

[clameter@sgi.com]

[-- Attachment #1: memless_thisnode_fix --]
[-- Type: text/plain, Size: 5355 bytes --]

GFP_THISNODE checks that the zone selected is within the pgdat (node) of the
first zone of a nodelist. That only works if the node has memory. A
memoryless node will have its first node on another pgdat (node).

GFP_THISNODE currently will return simply memory on the first pgdat.
Thus it is returning memory on other nodes. GFP_THISNODE should fail
if there is no local memory on a node.


Add a new set of zonelists for each node that only contain the nodes
that belong to the zones itself so that no fallback is possible.

Then modify gfp_type to pickup the right zone based on the presence
of __GFP_THISNODE.

Drop the existing GFP_THISNODE checks from the page_allocators hot path.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Nishanth Aravamudan <nacc@us.ibm.com>

Index: linux-2.6.22-rc4-mm2/include/linux/gfp.h
===================================================================
--- linux-2.6.22-rc4-mm2.orig/include/linux/gfp.h	2007-06-18 11:46:24.000000000 -0700
+++ linux-2.6.22-rc4-mm2/include/linux/gfp.h	2007-06-18 11:47:11.000000000 -0700
@@ -116,22 +116,28 @@ static inline int allocflags_to_migratet
 
 static inline enum zone_type gfp_zone(gfp_t flags)
 {
+	int base = 0;
+
+#ifdef CONFIG_NUMA
+	if (flags & __GFP_THISNODE)
+		base = MAX_NR_ZONES;
+#endif
 #ifdef CONFIG_ZONE_DMA
 	if (flags & __GFP_DMA)
-		return ZONE_DMA;
+		return base + ZONE_DMA;
 #endif
 #ifdef CONFIG_ZONE_DMA32
 	if (flags & __GFP_DMA32)
-		return ZONE_DMA32;
+		return base + ZONE_DMA32;
 #endif
 	if ((flags & (__GFP_HIGHMEM | __GFP_MOVABLE)) ==
 			(__GFP_HIGHMEM | __GFP_MOVABLE))
-		return ZONE_MOVABLE;
+		return base + ZONE_MOVABLE;
 #ifdef CONFIG_HIGHMEM
 	if (flags & __GFP_HIGHMEM)
-		return ZONE_HIGHMEM;
+		return base + ZONE_HIGHMEM;
 #endif
-	return ZONE_NORMAL;
+	return base + ZONE_NORMAL;
 }
 
 static inline gfp_t set_migrateflags(gfp_t gfp, gfp_t migrate_flags)
Index: linux-2.6.22-rc4-mm2/mm/page_alloc.c
===================================================================
--- linux-2.6.22-rc4-mm2.orig/mm/page_alloc.c	2007-06-18 11:46:26.000000000 -0700
+++ linux-2.6.22-rc4-mm2/mm/page_alloc.c	2007-06-18 11:48:32.000000000 -0700
@@ -1430,9 +1430,6 @@ zonelist_scan:
 			!zlc_zone_worth_trying(zonelist, z, allowednodes))
 				continue;
 		zone = *z;
-		if (unlikely(NUMA_BUILD && (gfp_mask & __GFP_THISNODE) &&
-			zone->zone_pgdat != zonelist->zones[0]->zone_pgdat))
-				break;
 		if ((alloc_flags & ALLOC_CPUSET) &&
 			!cpuset_zone_allowed_softwall(zone, gfp_mask))
 				goto try_next_zone;
@@ -1553,7 +1550,10 @@ restart:
 	z = zonelist->zones;  /* the list of zones suitable for gfp_mask */
 
 	if (unlikely(*z == NULL)) {
-		/* Should this ever happen?? */
+		/*
+		 * Happens if we have an empty zonelist as a result of
+		 * GFP_THISNODE being used on a memoryless node
+		 */
 		return NULL;
 	}
 
@@ -2151,6 +2151,22 @@ static void build_zonelists_in_node_orde
 }
 
 /*
+ * Build gfp_thisnode zonelists
+ */
+static void build_thisnode_zonelists(pg_data_t *pgdat)
+{
+	enum zone_type i;
+	int j;
+	struct zonelist *zonelist;
+
+	for (i = 0; i < MAX_NR_ZONES; i++) {
+		zonelist = pgdat->node_zonelists + MAX_NR_ZONES + i;
+ 		j = build_zonelists_node(pgdat, zonelist, 0, i);
+		zonelist->zones[j] = NULL;
+	}
+}
+
+/*
  * Build zonelists ordered by zone and nodes within zones.
  * This results in conserving DMA zone[s] until all Normal memory is
  * exhausted, but results in overflowing to remote node while memory
@@ -2254,7 +2270,7 @@ static void build_zonelists(pg_data_t *p
 	int order = current_zonelist_order;
 
 	/* initialize zonelists */
-	for (i = 0; i < MAX_NR_ZONES; i++) {
+	for (i = 0; i < 2 * MAX_NR_ZONES; i++) {
 		zonelist = pgdat->node_zonelists + i;
 		zonelist->zones[0] = NULL;
 	}
@@ -2299,6 +2315,8 @@ static void build_zonelists(pg_data_t *p
 		/* calculate node order -- i.e., DMA last! */
 		build_zonelists_in_zone_order(pgdat, j);
 	}
+
+	build_thisnode_zonelists(pgdat);
 }
 
 /* Construct the zonelist performance cache - see further mmzone.h */
Index: linux-2.6.22-rc4-mm2/include/linux/mmzone.h
===================================================================
--- linux-2.6.22-rc4-mm2.orig/include/linux/mmzone.h	2007-06-18 11:46:24.000000000 -0700
+++ linux-2.6.22-rc4-mm2/include/linux/mmzone.h	2007-06-18 11:47:11.000000000 -0700
@@ -356,6 +356,7 @@ struct zone {
 #define MAX_ZONES_PER_ZONELIST (MAX_NUMNODES * MAX_NR_ZONES)
 
 #ifdef CONFIG_NUMA
+#define MAX_ZONELISTS (2 * MAX_NR_ZONES)
 /*
  * We cache key information from each zonelist for smaller cache
  * footprint when scanning for free pages in get_page_from_freelist().
@@ -421,6 +422,7 @@ struct zonelist_cache {
 	unsigned long last_full_zap;		/* when last zap'd (jiffies) */
 };
 #else
+#define MAX_ZONELISTS MAX_NR_ZONES
 struct zonelist_cache;
 #endif
 
@@ -469,7 +471,7 @@ extern struct page *mem_map;
 struct bootmem_data;
 typedef struct pglist_data {
 	struct zone node_zones[MAX_NR_ZONES];
-	struct zonelist node_zonelists[MAX_NR_ZONES];
+	struct zonelist node_zonelists[MAX_ZONELISTS];
 	int nr_zones;
 #ifdef CONFIG_FLAT_NODE_MEM_MAP
 	struct page *node_mem_map;

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