Re: NUMA policy issues with ZONE_MOVABLE

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Wed, 25 Jul 2007 12:31:21 -0700 (PDT)
Christoph Lameter <clameter@sgi.com> wrote:
> So for a __GFP_MOVABLE alloc we would scan all zones and for 
> policy_zone just the policy zone.
> 
> Lee should probably also review this in detail since he has recent 
> experience fiddling around with memory policies. Paul has also 
> experience in this area.
> 
> Maybe this can actually  help to deal with some of the corner cases of 
> memory policies (just hope the performance impact is not significant).
> 
> 
Hmm,  How about following patch ? (not tested, just an idea).
I'm sorry if I misunderstand concept ot policy_zone.

==
Index: linux-2.6.23-rc1/include/linux/mempolicy.h
===================================================================
--- linux-2.6.23-rc1.orig/include/linux/mempolicy.h
+++ linux-2.6.23-rc1/include/linux/mempolicy.h
@@ -162,14 +162,11 @@ extern struct zonelist *huge_zonelist(st
 		unsigned long addr, gfp_t gfp_flags);
 extern unsigned slab_node(struct mempolicy *policy);
 
+/*
+ * The smalles zone_idx which all nodes can offer against GFP_xxx
+ */
 extern enum zone_type policy_zone;
 
-static inline void check_highest_zone(enum zone_type k)
-{
-	if (k > policy_zone)
-		policy_zone = k;
-}
-
 int do_migrate_pages(struct mm_struct *mm,
 	const nodemask_t *from_nodes, const nodemask_t *to_nodes, int flags);
 
Index: linux-2.6.23-rc1/mm/page_alloc.c
===================================================================
--- linux-2.6.23-rc1.orig/mm/page_alloc.c
+++ linux-2.6.23-rc1/mm/page_alloc.c
@@ -1648,7 +1648,6 @@ static int build_zonelists_node(pg_data_
 		zone = pgdat->node_zones + zone_type;
 		if (populated_zone(zone)) {
 			zonelist->zones[nr_zones++] = zone;
-			check_highest_zone(zone_type);
 		}
 
 	} while (zone_type);
@@ -1857,7 +1856,6 @@ static void build_zonelists_in_zone_orde
 				z = &NODE_DATA(node)->node_zones[zone_type];
 				if (populated_zone(z)) {
 					zonelist->zones[pos++] = z;
-					check_highest_zone(zone_type);
 				}
 			}
 		}
@@ -1934,6 +1932,7 @@ static void build_zonelists(pg_data_t *p
 	int local_node, prev_node;
 	struct zonelist *zonelist;
 	int order = current_zonelist_order;
+	int highest_zone;
 
 	/* initialize zonelists */
 	for (i = 0; i < MAX_NR_ZONES; i++) {
@@ -1981,6 +1980,32 @@ static void build_zonelists(pg_data_t *p
 		/* calculate node order -- i.e., DMA last! */
 		build_zonelists_in_zone_order(pgdat, j);
 	}
+	/*
+	 * Find the lowest zone where mempolicy (MBID) can work well.
+ 	 */
+	highest_zone = 0;
+	policy_zone = -1;
+	for (i = 0; i < MAX_NR_ZONES; i++) {
+		struct zone *first_zone;
+		int success = 1;
+		for_each_node_state(node, N_MEMORY) {
+			first_zone = NODE_DATA(node)->node_zonelists[i][0];
+			if (zone_idx(first_zone) > highest_zone)
+				highest_zone = zone_idx(first_zone);
+			if (first_zone->zone_pgdat != NODE_DATA(node)) {
+				/* This node cannot offer right pages for this
+				   GFP */
+				success = 0;
+				break;
+			}
+		}
+		if (success) {
+			policy_zone = i;
+			break;
+		}
+	}
+	if (policy_zone == -1)
+		policy_zone = highest_zone;
 }
 
 /* Construct the zonelist performance cache - see further mmzone.h */

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