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slab: shrink sizeof(struct kmem_cache)

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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>
This commit is contained in:
Eric Dumazet
2011-07-20 19:04:23 +02:00
committed by Pekka Enberg
parent c225150b86
commit b56efcf0a4
2 changed files with 19 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
mm/slab.c
View File

@@ -574,7 +574,9 @@ static struct arraycache_init initarray_generic =
{ {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 @@ void __init kmem_cache_init(void)
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 @@ kmem_cache_create (const char *name, size_t size, size_t align,
if (!cachep)
goto oops;
cachep->nodelists = (struct kmem_list3 **)&cachep->array[nr_cpu_ids];
#if DEBUG
cachep->obj_size = size;