slub: move kmem_cache_node into it's own cacheline

This patch is meant to improve the performance of SLUB by moving the local
kmem_cache_node lock into it's own cacheline separate from kmem_cache.
This is accomplished by simply removing the local_node when NUMA is enabled.

On my system with 2 nodes I saw around a 5% performance increase w/
hackbench times dropping from 6.2 seconds to 5.9 seconds on average.  I
suspect the performance gain would increase as the number of nodes
increases, but I do not have the data to currently back that up.

Bugzilla-Reference: http://bugzilla.kernel.org/show_bug.cgi?id=15713
Cc: <stable@kernel.org>
Reported-by: Alex Shi <alex.shi@intel.com>
Tested-by: Alex Shi <alex.shi@intel.com>
Acked-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

2 files changed, 14 insertions, 28 deletions

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 55695c8d2f8a..6ac37664e8fe 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -75,12 +75,6 @@ struct kmem_cache {
         int offset;             /* Free pointer offset. */
         struct kmem_cache_order_objects oo;
 
-        /*
-         * Avoid an extra cache line for UP, SMP and for the node local to
-         * struct kmem_cache.
-         */
-        struct kmem_cache_node local_node;
-
         /* Allocation and freeing of slabs */
         struct kmem_cache_order_objects max;
         struct kmem_cache_order_objects min;
@@ -102,6 +96,9 @@ struct kmem_cache {
          */
         int remote_node_defrag_ratio;
         struct kmem_cache_node *node[MAX_NUMNODES];
+#else
+        /* Avoid an extra cache line for UP */
+        struct kmem_cache_node local_node;
 #endif
 };
 
diff --git a/mm/slub.c b/mm/slub.c
index e46e3129697d..c2d6e6951f33 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2133,7 +2133,7 @@ static void free_kmem_cache_nodes(struct kmem_cache *s)
 
         for_each_node_state(node, N_NORMAL_MEMORY) {
                 struct kmem_cache_node *n = s->node[node];
-                if (n && n != &s->local_node)
+                if (n)
                         kmem_cache_free(kmalloc_caches, n);
                 s->node[node] = NULL;
         }
@@ -2142,33 +2142,22 @@ static void free_kmem_cache_nodes(struct kmem_cache *s)
 static int init_kmem_cache_nodes(struct kmem_cache *s, gfp_t gfpflags)
 {
         int node;
-        int local_node;
-
-        if (slab_state >= UP && (s < kmalloc_caches ||
-                        s >= kmalloc_caches + KMALLOC_CACHES))
-                local_node = page_to_nid(virt_to_page(s));
-        else
-                local_node = 0;
 
         for_each_node_state(node, N_NORMAL_MEMORY) {
                 struct kmem_cache_node *n;
 
-                if (local_node == node)
-                        n = &s->local_node;
-                else {
-                        if (slab_state == DOWN) {
-                                early_kmem_cache_node_alloc(gfpflags, node);
-                                continue;
-                        }
-                        n = kmem_cache_alloc_node(kmalloc_caches,
-                                                        gfpflags, node);
-
-                        if (!n) {
-                                free_kmem_cache_nodes(s);
-                                return 0;
-                        }
+                if (slab_state == DOWN) {
+                        early_kmem_cache_node_alloc(gfpflags, node);
+                        continue;
+                }
+                n = kmem_cache_alloc_node(kmalloc_caches,
+                                                gfpflags, node);
 
+                if (!n) {
+                        free_kmem_cache_nodes(s);
+                        return 0;
                 }
+
                 s->node[node] = n;
                 init_kmem_cache_node(n, s);
         }