Using one zonelist per node requires very frequent use of zone_idx(). This
is costly as it involves a lookup of another structure and a substraction
operation. struct zone is aligned on a node-interleave boundary so the
pointer values of plenty of 0's at the least significant bits of the address.

This patch embeds the zone_id of a zone in the zonelist->zones pointers.
The real zone pointer is found using the zonelist_zone() helper function.
The ID of the zone is found using zonelist_zone_idx().  To avoid accidental
references, the zones field is renamed to _zones.
Signed-off-by: Mel Gorman <[EMAIL PROTECTED]>
---

 include/linux/mmzone.h |   59 ++++++++++++++++++++++++++++++++++++++++----
 mm/mempolicy.c         |   22 ++++++++--------
 mm/page_alloc.c        |   36 +++++++++++++-------------
 mm/vmstat.c            |    4 +-
 4 files changed, 85 insertions(+), 36 deletions(-)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.23-rc1-mm2-010_use_zonelist/include/linux/mmzone.h 
linux-2.6.23-rc1-mm2-015_zoneid_zonelist/include/linux/mmzone.h
--- linux-2.6.23-rc1-mm2-010_use_zonelist/include/linux/mmzone.h        
2007-08-09 15:08:15.000000000 +0100
+++ linux-2.6.23-rc1-mm2-015_zoneid_zonelist/include/linux/mmzone.h     
2007-08-09 18:00:41.000000000 +0100
@@ -436,7 +436,9 @@ struct zonelist_cache;
 
 struct zonelist {
        struct zonelist_cache *zlcache_ptr;                  // NULL or &zlcache
-       struct zone *zones[MAX_ZONES_PER_ZONELIST + 1];      // NULL delimited
+       struct zone *_zones[MAX_ZONES_PER_ZONELIST + 1];     // NULL delimited
+                                                            // Access with
+                                                            // zonelist_zone()
 #ifdef CONFIG_NUMA
        struct zonelist_cache zlcache;                       // optional ...
 #endif
@@ -676,12 +678,57 @@ static inline struct zonelist *node_zone
        return &NODE_DATA(nid)->node_zonelist;
 }
 
+#if defined(CONFIG_SMP) && INTERNODE_CACHE_SHIFT > ZONES_SHIFT
+
+/* Similar to ZONES_MASK but is not available in this context */
+#define ZONELIST_ZONEIDX_MASK ((1UL << ZONES_SHIFT) - 1)
+
+/* zone_id is small enough to fit at bottom of zone pointer in zonelist */
+static inline struct zone *zonelist_zone(struct zone *zone)
+{
+       return (struct zone *)((unsigned long)zone & ~ZONELIST_ZONEIDX_MASK);
+}
+
+
+static inline int zonelist_zone_idx(struct zone *zone)
+{
+       /* ZONES_MASK not available in this context */
+       return (unsigned long)zone & ZONELIST_ZONEIDX_MASK;
+}
+
+static inline struct zone *encode_zone_idx(struct zone *zone)
+{
+       struct zone *encoded;
+
+       encoded = (struct zone *)((unsigned long)zone | zone_idx(zone));
+       BUG_ON(zonelist_zone(encoded) != zone);
+       return encoded;
+}
+#else
+static inline struct zone *zonelist_zone(struct zone *zone)
+{
+       return zone;
+}
+
+static inline int zonelist_zone_idx(struct zone *zone)
+{
+       return zone_idx(zone);
+}
+
+static inline struct zone *encode_zone_idx(struct zone *zone)
+{
+       return zone;
+}
+#endif
+
 /* Returns the first zone at or below highest_zoneidx in a zonelist */
 static inline struct zone **first_zones_zonelist(struct zonelist *zonelist,
                                        enum zone_type highest_zoneidx)
 {
        struct zone **z;
-       for (z = zonelist->zones; *z && zone_idx(*z) > highest_zoneidx; z++);
+       for (z = zonelist->_zones;
+               *z && zonelist_zone_idx(*z) > highest_zoneidx;
+               z++);
        return z;
 }
 
@@ -689,7 +736,9 @@ static inline struct zone **first_zones_
 static inline struct zone **next_zones_zonelist(struct zone **z,
                                        enum zone_type highest_zoneidx)
 {
-       for (++z; *z && zone_idx(*z) > highest_zoneidx; z++);
+       for (++z;
+               *z && zonelist_zone_idx(*z) > highest_zoneidx;
+               z++);
        return z;
 }
 
@@ -703,9 +752,9 @@ static inline struct zone **next_zones_z
  * This iterator iterates though all zones at or below a given zone index.
  */
 #define for_each_zone_zonelist(zone, z, zlist, highidx) \
-       for (z = first_zones_zonelist(zlist, highidx), zone = *z;       \
+       for (z = first_zones_zonelist(zlist, highidx), zone = 
zonelist_zone(*z);        \
                zone;                                                   \
-               z = next_zones_zonelist(z, highidx), zone = *z)
+               z = next_zones_zonelist(z, highidx), zone = zonelist_zone(*z))
 
 #ifdef CONFIG_SPARSEMEM
 #include <asm/sparsemem.h>
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.23-rc1-mm2-010_use_zonelist/mm/mempolicy.c 
linux-2.6.23-rc1-mm2-015_zoneid_zonelist/mm/mempolicy.c
--- linux-2.6.23-rc1-mm2-010_use_zonelist/mm/mempolicy.c        2007-08-09 
18:34:00.000000000 +0100
+++ linux-2.6.23-rc1-mm2-015_zoneid_zonelist/mm/mempolicy.c     2007-08-09 
18:33:51.000000000 +0100
@@ -156,7 +156,7 @@ static struct zonelist *bind_zonelist(no
                for_each_node_mask(nd, *nodes) { 
                        struct zone *z = &NODE_DATA(nd)->node_zones[k];
                        if (z->present_pages > 0) 
-                               zl->zones[num++] = z;
+                               zl->_zones[num++] = encode_zone_idx(z);
                }
                if (k == 0)
                        break;
@@ -166,7 +166,7 @@ static struct zonelist *bind_zonelist(no
                kfree(zl);
                return ERR_PTR(-EINVAL);
        }
-       zl->zones[num] = NULL;
+       zl->_zones[num] = NULL;
        return zl;
 }
 
@@ -486,8 +486,8 @@ static void get_zonemask(struct mempolic
        nodes_clear(*nodes);
        switch (p->policy) {
        case MPOL_BIND:
-               for (i = 0; p->v.zonelist->zones[i]; i++)
-                       node_set(zone_to_nid(p->v.zonelist->zones[i]),
+               for (i = 0; p->v.zonelist->_zones[i]; i++)
+                       
node_set(zone_to_nid(zonelist_zone(p->v.zonelist->_zones[i])),
                                *nodes);
                break;
        case MPOL_DEFAULT:
@@ -1154,7 +1154,7 @@ unsigned slab_node(struct mempolicy *pol
                 * Follow bind policy behavior and start allocation at the
                 * first node.
                 */
-               return zone_to_nid(policy->v.zonelist->zones[0]);
+               return 
zone_to_nid(zonelist_zone(policy->v.zonelist->_zones[0]));
 
        case MPOL_PREFERRED:
                if (policy->v.preferred_node >= 0)
@@ -1232,7 +1232,7 @@ static struct page *alloc_page_interleav
 
        zl = node_zonelist(nid);
        page = __alloc_pages(gfp, order, zl);
-       if (page && page_zone(page) == zl->zones[0])
+       if (page && page_zone(page) == zonelist_zone(zl->_zones[0]))
                inc_zone_page_state(page, NUMA_INTERLEAVE_HIT);
        return page;
 }
@@ -1356,10 +1356,10 @@ int __mpol_equal(struct mempolicy *a, st
                return a->v.preferred_node == b->v.preferred_node;
        case MPOL_BIND: {
                int i;
-               for (i = 0; a->v.zonelist->zones[i]; i++)
-                       if (a->v.zonelist->zones[i] != b->v.zonelist->zones[i])
+               for (i = 0; a->v.zonelist->_zones[i]; i++)
+                       if (zonelist_zone(a->v.zonelist->_zones[i]) != 
zonelist_zone(b->v.zonelist->_zones[i]))
                                return 0;
-               return b->v.zonelist->zones[i] == NULL;
+               return b->v.zonelist->_zones[i] == NULL;
        }
        default:
                BUG();
@@ -1682,8 +1682,8 @@ static void mpol_rebind_policy(struct me
                struct zonelist *zonelist;
 
                nodes_clear(nodes);
-               for (z = pol->v.zonelist->zones; *z; z++)
-                       node_set(zone_to_nid(*z), nodes);
+               for (z = pol->v.zonelist->_zones; *z; z++)
+                       node_set(zone_to_nid(zonelist_zone(*z)), nodes);
                nodes_remap(tmp, nodes, *mpolmask, *newmask);
                nodes = tmp;
 
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.23-rc1-mm2-010_use_zonelist/mm/page_alloc.c 
linux-2.6.23-rc1-mm2-015_zoneid_zonelist/mm/page_alloc.c
--- linux-2.6.23-rc1-mm2-010_use_zonelist/mm/page_alloc.c       2007-08-09 
15:04:19.000000000 +0100
+++ linux-2.6.23-rc1-mm2-015_zoneid_zonelist/mm/page_alloc.c    2007-08-09 
15:52:12.000000000 +0100
@@ -1360,7 +1360,7 @@ static int zlc_zone_worth_trying(struct 
        if (!zlc)
                return 1;
 
-       i = z - zonelist->zones;
+       i = z - zonelist->_zones;
        n = zlc->z_to_n[i];
 
        /* This zone is worth trying if it is allowed but not full */
@@ -1381,7 +1381,7 @@ static void zlc_mark_zone_full(struct zo
        if (!zlc)
                return;
 
-       i = z - zonelist->zones;
+       i = z - zonelist->_zones;
 
        set_bit(i, zlc->fullzones);
 }
@@ -1414,7 +1414,7 @@ get_page_from_freelist(gfp_t gfp_mask, u
 {
        struct zone **z;
        struct page *page = NULL;
-       int classzone_idx = zone_idx(zonelist->zones[0]);
+       int classzone_idx = zonelist_zone_idx(zonelist->_zones[0]);
        struct zone *zone;
        enum zone_type high_zoneidx = gfp_zone(gfp_mask);
        nodemask_t *allowednodes = NULL;/* zonelist_cache approximation */
@@ -1431,7 +1431,7 @@ zonelist_scan:
                        !zlc_zone_worth_trying(zonelist, z, allowednodes))
                                continue;
                if (unlikely(NUMA_BUILD && (gfp_mask & __GFP_THISNODE) &&
-                       zone->zone_pgdat != zonelist->zones[0]->zone_pgdat))
+                       zone->zone_pgdat != 
zonelist_zone(zonelist->_zones[0])->zone_pgdat))
                                break;
                if ((alloc_flags & ALLOC_CPUSET) &&
                        !cpuset_zone_allowed_softwall(zone, gfp_mask))
@@ -1554,9 +1554,9 @@ __alloc_pages(gfp_t gfp_mask, unsigned i
                return NULL;
 
 restart:
-       z = zonelist->zones;  /* the list of zones suitable for gfp_mask */
+       z = zonelist->_zones;  /* the list of zones suitable for gfp_mask */
 
-       if (unlikely(*z == NULL)) {
+       if (unlikely(zonelist_zone(*z) == NULL)) {
                /* Should this ever happen?? */
                return NULL;
        }
@@ -1577,8 +1577,8 @@ restart:
        if (NUMA_BUILD && (gfp_mask & GFP_THISNODE) == GFP_THISNODE)
                goto nopage;
 
-       for (z = zonelist->zones; *z; z++)
-               wakeup_kswapd(*z, order);
+       for (z = zonelist->_zones; *z; z++)
+               wakeup_kswapd(zonelist_zone(*z), order);
 
        /*
         * OK, we're below the kswapd watermark and have kicked background
@@ -1974,7 +1974,7 @@ static int build_zonelists_node(pg_data_
                zone_type--;
                zone = pgdat->node_zones + zone_type;
                if (populated_zone(zone)) {
-                       zonelist->zones[nr_zones++] = zone;
+                       zonelist->_zones[nr_zones++] = encode_zone_idx(zone);
                        check_highest_zone(zone_type);
                }
 
@@ -2150,10 +2150,10 @@ static void build_zonelists_in_node_orde
        struct zonelist *zonelist;
 
        zonelist = &pgdat->node_zonelist;
-       for (j = 0; zonelist->zones[j] != NULL; j++)
+       for (j = 0; zonelist->_zones[j] != NULL; j++)
                ;
        j = build_zonelists_node(NODE_DATA(node), zonelist, j, MAX_NR_ZONES-1);
-       zonelist->zones[j] = NULL;
+       zonelist->_zones[j] = NULL;
 }
 
 /*
@@ -2178,12 +2178,12 @@ static void build_zonelists_in_zone_orde
                        node = node_order[j];
                        z = &NODE_DATA(node)->node_zones[zone_type];
                        if (populated_zone(z)) {
-                               zonelist->zones[pos++] = z;
+                               zonelist->_zones[pos++] = encode_zone_idx(z);
                                check_highest_zone(zone_type);
                        }
                }
        }
-       zonelist->zones[pos] = NULL;
+       zonelist->_zones[pos] = NULL;
 }
 
 static int default_zonelist_order(void)
@@ -2257,7 +2257,7 @@ static void build_zonelists(pg_data_t *p
 
        /* initialize zonelist */
        zonelist = &pgdat->node_zonelist;
-       zonelist->zones[0] = NULL;
+       zonelist->_zones[0] = NULL;
 
        /* NUMA-aware ordering of nodes */
        local_node = pgdat->node_id;
@@ -2304,7 +2304,6 @@ static void build_zonelists(pg_data_t *p
 /* Construct the zonelist performance cache - see further mmzone.h */
 static void build_zonelist_cache(pg_data_t *pgdat)
 {
-       int i;
        struct zonelist *zonelist;
        struct zonelist_cache *zlc;
        struct zone **z;
@@ -2312,8 +2311,9 @@ static void build_zonelist_cache(pg_data
        zonelist = &pgdat->node_zonelist;
        zonelist->zlcache_ptr = zlc = &zonelist->zlcache;
        bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
-       for (z = zonelist->zones; *z; z++)
-               zlc->z_to_n[z - zonelist->zones] = zone_to_nid(*z);
+       for (z = zonelist->_zones; *z; z++)
+               zlc->z_to_n[z - zonelist->_zones] =
+                       zone_to_nid(zonelist_zone(*z));
 }
 
 
@@ -2356,7 +2356,7 @@ static void build_zonelists(pg_data_t *p
                                                                MAX_NR_ZONES-1);
        }
 
-       zonelist->zones[j] = NULL;
+       zonelist->_zones[j] = NULL;
 }
 
 /* non-NUMA variant of zonelist performance cache - just NULL zlcache_ptr */
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff 
linux-2.6.23-rc1-mm2-010_use_zonelist/mm/vmstat.c 
linux-2.6.23-rc1-mm2-015_zoneid_zonelist/mm/vmstat.c
--- linux-2.6.23-rc1-mm2-010_use_zonelist/mm/vmstat.c   2007-08-07 
14:45:11.000000000 +0100
+++ linux-2.6.23-rc1-mm2-015_zoneid_zonelist/mm/vmstat.c        2007-08-09 
15:52:12.000000000 +0100
@@ -365,11 +365,11 @@ void refresh_cpu_vm_stats(int cpu)
  */
 void zone_statistics(struct zonelist *zonelist, struct zone *z)
 {
-       if (z->zone_pgdat == zonelist->zones[0]->zone_pgdat) {
+       if (z->zone_pgdat == zonelist_zone(zonelist->_zones[0])->zone_pgdat) {
                __inc_zone_state(z, NUMA_HIT);
        } else {
                __inc_zone_state(z, NUMA_MISS);
-               __inc_zone_state(zonelist->zones[0], NUMA_FOREIGN);
+               __inc_zone_state(zonelist_zone(zonelist->_zones[0]), 
NUMA_FOREIGN);
        }
        if (z->node == numa_node_id())
                __inc_zone_state(z, NUMA_LOCAL);
-
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