slab: shrink sizeof(struct kmem_cache)
Reduce high order allocations for some setups.
(NR_CPUS=4096 -> we need 64KB per kmem_cache struct)
We now allocate exact needed size (using nr_cpu_ids and nr_node_ids)
This also makes code a bit smaller on x86_64, since some field offsets
are less than the 127 limit :
Before patch :
# size mm/slab.o
text data bss dec hex filename
22605 361665 32 384302 5dd2e mm/slab.o
After patch :
# size mm/slab.o
text data bss dec hex filename
22349 353473 8224 384046 5dc2e mm/slab.o
CC: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
diff --git a/mm/slab.c b/mm/slab.c
index ef8ceb7..c3cb359 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -574,7 +574,9 @@
{ {0, BOOT_CPUCACHE_ENTRIES, 1, 0} };
/* internal cache of cache description objs */
+static struct kmem_list3 *cache_cache_nodelists[MAX_NUMNODES];
static struct kmem_cache cache_cache = {
+ .nodelists = cache_cache_nodelists,
.batchcount = 1,
.limit = BOOT_CPUCACHE_ENTRIES,
.shared = 1,
@@ -1492,11 +1494,10 @@
cache_cache.nodelists[node] = &initkmem_list3[CACHE_CACHE + node];
/*
- * struct kmem_cache size depends on nr_node_ids, which
- * can be less than MAX_NUMNODES.
+ * struct kmem_cache size depends on nr_node_ids & nr_cpu_ids
*/
- cache_cache.buffer_size = offsetof(struct kmem_cache, nodelists) +
- nr_node_ids * sizeof(struct kmem_list3 *);
+ cache_cache.buffer_size = offsetof(struct kmem_cache, array[nr_cpu_ids]) +
+ nr_node_ids * sizeof(struct kmem_list3 *);
#if DEBUG
cache_cache.obj_size = cache_cache.buffer_size;
#endif
@@ -2308,6 +2309,7 @@
if (!cachep)
goto oops;
+ cachep->nodelists = (struct kmem_list3 **)&cachep->array[nr_cpu_ids];
#if DEBUG
cachep->obj_size = size;