slub: Get rid of the node field

The node field is always page_to_nid(c->page). So its rather easy to
replace. Note that there maybe slightly more overhead in various hot paths
due to the need to shift the bits from page->flags. However, that is mostly
compensated for by a smaller footprint of the kmem_cache_cpu structure (this
patch reduces that to 3 words per cache) which allows better caching.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

1 files changed, 16 insertions, 19 deletions

diff --git a/mm/slub.c b/mm/slub.c
index b29246bc7392..aed879276410 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1561,7 +1561,6 @@ static void *get_partial_node(struct kmem_cache *s,
 
                 if (!object) {
                         c->page = page;
-                        c->node = page_to_nid(page);
                         stat(s, ALLOC_FROM_PARTIAL);
                         object = t;
                         available =  page->objects - page->inuse;
@@ -2057,7 +2056,7 @@ static void flush_all(struct kmem_cache *s)
 static inline int node_match(struct kmem_cache_cpu *c, int node)
 {
 #ifdef CONFIG_NUMA
-        if (node != NUMA_NO_NODE && c->node != node)
+        if (node != NUMA_NO_NODE && page_to_nid(c->page) != node)
                 return 0;
 #endif
         return 1;
@@ -2152,7 +2151,6 @@ static inline void *new_slab_objects(struct kmem_cache *s, gfp_t flags,
                 page->freelist = NULL;
 
                 stat(s, ALLOC_SLAB);
-                c->node = page_to_nid(page);
                 c->page = page;
                 *pc = c;
         } else
@@ -2269,7 +2267,6 @@ new_slab:
         if (c->partial) {
                 c->page = c->partial;
                 c->partial = c->page->next;
-                c->node = page_to_nid(c->page);
                 stat(s, CPU_PARTIAL_ALLOC);
                 c->freelist = NULL;
                 goto redo;
@@ -2294,7 +2291,6 @@ new_slab:
 
         c->freelist = get_freepointer(s, freelist);
         deactivate_slab(s, c);
-        c->node = NUMA_NO_NODE;
         local_irq_restore(flags);
         return freelist;
 }
@@ -4507,30 +4503,31 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
 
                 for_each_possible_cpu(cpu) {
                         struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
-                        int node = ACCESS_ONCE(c->node);
+                        int node;
                         struct page *page;
 
-                        if (node < 0)
-                                continue;
                         page = ACCESS_ONCE(c->page);
-                        if (page) {
-                                if (flags & SO_TOTAL)
-                                        x = page->objects;
-                                else if (flags & SO_OBJECTS)
-                                        x = page->inuse;
-                                else
-                                        x = 1;
+                        if (!page)
+                                continue;
 
-                                total += x;
-                                nodes[node] += x;
-                        }
-                        page = c->partial;
+                        node = page_to_nid(page);
+                        if (flags & SO_TOTAL)
+                                x = page->objects;
+                        else if (flags & SO_OBJECTS)
+                                x = page->inuse;
+                        else
+                                x = 1;
+
+                        total += x;
+                        nodes[node] += x;
 
+                        page = ACCESS_ONCE(c->partial);
                         if (page) {
                                 x = page->pobjects;
                                 total += x;
                                 nodes[node] += x;
                         }
+
                         per_cpu[node]++;
                 }
         }