From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Lameter Subject: [patch 04/10] SLUB: Avoid checking for a valid object before zeroing on the fast path Date: Sat, 27 Oct 2007 20:32:00 -0700 Message-ID: <20071028033259.263401839@sgi.com> References: <20071028033156.022983073@sgi.com> Return-path: Content-Disposition: inline; filename=slub_slab_alloc_move_oom Sender: linux-kernel-owner@vger.kernel.org To: Matthew Wilcox Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Pekka Enberg List-Id: linux-mm.kvack.org The fast path always results in a valid object. Move the check for the NULL pointer to the slow branch that calls __slab_alloc. Only __slab_alloc can return NULL if there is no memory available anymore and that case is exceedingly rare. Signed-off-by: Christoph Lameter --- mm/slub.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) Index: linux-2.6/mm/slub.c =================================================================== --- linux-2.6.orig/mm/slub.c 2007-10-25 19:37:38.000000000 -0700 +++ linux-2.6/mm/slub.c 2007-10-25 19:38:14.000000000 -0700 @@ -1573,19 +1573,22 @@ static void __always_inline *slab_alloc( local_irq_save(flags); c = get_cpu_slab(s, smp_processor_id()); - if (unlikely(!c->freelist || !node_match(c, node))) + if (unlikely(!c->freelist || !node_match(c, node))) { object = __slab_alloc(s, gfpflags, node, addr, c); - - else { + if (unlikely(!object)) { + local_irq_restore(flags); + goto out; + } + } else { object = c->freelist; c->freelist = object[c->offset]; } local_irq_restore(flags); - if (unlikely((gfpflags & __GFP_ZERO) && object)) + if (unlikely((gfpflags & __GFP_ZERO))) memset(object, 0, c->objsize); - +out: return object; } --