We touch a cacheline in the kmem_cache structure for zeroing to get the size. However, the hot paths in slab_alloc and slab_free do not reference any other fields in kmem_cache. Add a new field to kmem_cache_cpu that contains the object size. That cacheline must already be used. So we save one cacheline on every slab_alloc. We need to update the kmem_cache_cpu object size if an aliasing operation changes the objsize of an non debug slab. Signed-off-by: Christoph Lameter --- include/linux/slub_def.h | 1 + mm/slub.c | 14 ++++++++++++-- 2 files changed, 13 insertions(+), 2 deletions(-) Index: linux-2.6.22-rc6-mm1/include/linux/slub_def.h =================================================================== --- linux-2.6.22-rc6-mm1.orig/include/linux/slub_def.h 2007-07-07 13:56:24.000000000 -0700 +++ linux-2.6.22-rc6-mm1/include/linux/slub_def.h 2007-07-07 15:52:37.000000000 -0700 @@ -16,6 +16,7 @@ struct kmem_cache_cpu { struct page *page; int node; unsigned int offset; + unsigned int objsize; }; struct kmem_cache_node { Index: linux-2.6.22-rc6-mm1/mm/slub.c =================================================================== --- linux-2.6.22-rc6-mm1.orig/mm/slub.c 2007-07-07 13:56:24.000000000 -0700 +++ linux-2.6.22-rc6-mm1/mm/slub.c 2007-07-07 17:49:25.000000000 -0700 @@ -1571,7 +1571,7 @@ static void __always_inline *slab_alloc( local_irq_restore(flags); if (unlikely((gfpflags & __GFP_ZERO) && object)) - memset(object, 0, s->objsize); + memset(object, 0, c->objsize); return object; } @@ -1864,8 +1864,9 @@ static void init_kmem_cache_cpu(struct k { c->page = NULL; c->freelist = NULL; - c->offset = s->offset / sizeof(void *); c->node = 0; + c->offset = s->offset / sizeof(void *); + c->objsize = s->objsize; } static void init_kmem_cache_node(struct kmem_cache_node *n) @@ -3173,12 +3174,21 @@ struct kmem_cache *kmem_cache_create(con down_write(&slub_lock); s = find_mergeable(size, align, flags, ctor, ops); if (s) { + int cpu; + s->refcount++; /* * Adjust the object sizes so that we clear * the complete object on kzalloc. */ s->objsize = max(s->objsize, (int)size); + + /* + * And then we need to update the object size in the + * per cpu structures + */ + for_each_online_cpu(cpu) + get_cpu_slab(s, cpu)->objsize = s->objsize; s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *))); up_write(&slub_lock); -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/