From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx119.postini.com [74.125.245.119]) by kanga.kvack.org (Postfix) with SMTP id 3E2D76B00DD for ; Tue, 18 Sep 2012 11:28:21 -0400 (EDT) Date: Tue, 18 Sep 2012 15:28:19 +0000 From: Christoph Lameter Subject: Re: [PATCH v3 09/16] sl[au]b: always get the cache from its page in kfree In-Reply-To: <1347977530-29755-10-git-send-email-glommer@parallels.com> Message-ID: <00000139d9fe8595-8905906d-18ed-4d41-afdb-f4c632c2d50a-000000@email.amazonses.com> References: <1347977530-29755-1-git-send-email-glommer@parallels.com> <1347977530-29755-10-git-send-email-glommer@parallels.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Glauber Costa Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com, devel@openvz.org, Tejun Heo , linux-mm@kvack.org, Suleiman Souhlal , Frederic Weisbecker , Mel Gorman , David Rientjes , Pekka Enberg On Tue, 18 Sep 2012, Glauber Costa wrote: > index f2d760c..18de3f6 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -3938,9 +3938,12 @@ EXPORT_SYMBOL(__kmalloc); > * Free an object which was previously allocated from this > * cache. > */ > -void kmem_cache_free(struct kmem_cache *cachep, void *objp) > +void kmem_cache_free(struct kmem_cache *s, void *objp) > { > unsigned long flags; > + struct kmem_cache *cachep = virt_to_cache(objp); > + > + VM_BUG_ON(!slab_equal_or_parent(cachep, s)); > This is an extremely hot path of the kernel and you are adding significant processing. Check how the benchmarks are influenced by this change. virt_to_cache can be a bit expensive. > diff --git a/mm/slub.c b/mm/slub.c > index 4778548..a045dfc 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2604,7 +2604,9 @@ void kmem_cache_free(struct kmem_cache *s, void *x) > > page = virt_to_head_page(x); > > - slab_free(s, page, x, _RET_IP_); > + VM_BUG_ON(!slab_equal_or_parent(page->slab, s)); > + > + slab_free(page->slab, page, x, _RET_IP_); > Less of a problem here but you are eroding one advantage that slab has had in the past over slub in terms of freeing objects. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org