From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d12nrmr1607.megacenter.de.ibm.com (d12nrmr1607.megacenter.de.ibm.com [9.149.167.49]) by mtagate2.de.ibm.com (8.13.7/8.13.7) with ESMTP id k6Q8rhBQ117868 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=FAIL) for ; Wed, 26 Jul 2006 08:53:43 GMT Received: from d06av01.portsmouth.uk.ibm.com (d06av01.portsmouth.uk.ibm.com [9.149.37.212]) by d12nrmr1607.megacenter.de.ibm.com (8.13.6/NCO/VER7.0) with ESMTP id k6Q8uxpX103248 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 26 Jul 2006 10:57:00 +0200 Received: from d06av01.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av01.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id k6Q8rX0u030181 for ; Wed, 26 Jul 2006 09:53:33 +0100 Date: Wed, 26 Jul 2006 10:51:13 +0200 From: Heiko Carstens Subject: [patch 2/2] slab: always consider arch mandated alignment Message-ID: <20060726085113.GD9592@osiris.boeblingen.de.ibm.com> References: <20060722110601.GA9572@osiris.boeblingen.de.ibm.com> <20060722162607.GA10550@osiris.ibm.com> <20060723073500.GA10556@osiris.ibm.com> <20060723162427.GA10553@osiris.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060723162427.GA10553@osiris.ibm.com> Sender: owner-linux-mm@kvack.org From: Heiko Carstens Return-Path: To: Christoph Lameter Cc: Andrew Morton , linux-kernel@vger.kernel.org, Pekka Enberg , linux-mm@kvack.org, Martin Schwidefsky List-ID: Since ARCH_KMALLOC_MINALIGN didn't work on s390 I tried ARCH_SLAB_MINALIGN instead, just to find out that it didn't work too. In case of CONFIG_DEBUG_SLAB kmem_cache_create() creates caches with an alignment lesser than ARCH_SLAB_MINALIGN, which it shouldn't according to this comment in mm/slab.c : * Enforce a minimum alignment for all caches. * Intended for archs that get misalignment faults even for BYTES_PER_WORD * aligned buffers. Includes ARCH_KMALLOC_MINALIGN. * If possible: Do not enable this flag for CONFIG_DEBUG_SLAB, it disables * some debug features. For example the following might happen if kmem_cache_create() gets called with -- size: 64; align: 0; flags with SLAB_HWCACHE_ALIGN, SLAB_RED_ZONE and SLAB_STORE_USER set. ARCH_SLAB_MINALIGN is 8. These are the steps as numbered in kmem_cache_create() where 5) is after the "if (flags & SLAB_RED_ZONE)" statement. 1) align: 0 ralign 64 2) align: 0 ralign 64 3) align: 0 ralign 64 4) align: 64 ralign 64 5) align: 4 ralign 64 Note that in this case in step 2) the flags SLAB_RED_ZONE and SLAB_STORE_USER don't get masked out and that this causes an BYTES_PER_WORD alignment in step 5) which is lesser than ARCH_SLAB_MINALIGN. Cc: Christoph Lameter Cc: Pekka Enberg Signed-off-by: Heiko Carstens --- mm/slab.c | 3 +++ 1 files changed, 3 insertions(+) Index: linux-2.6/mm/slab.c =================================================================== --- linux-2.6.orig/mm/slab.c 2006-07-26 09:55:54.000000000 +0200 +++ linux-2.6/mm/slab.c 2006-07-26 09:57:07.000000000 +0200 @@ -2103,6 +2103,9 @@ if (ralign > BYTES_PER_WORD) flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER); } + if (BYTES_PER_WORD < ARCH_SLAB_MINALIGN) + flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER); + /* 3) caller mandated alignment: disables debug if necessary */ if (ralign < align) { ralign = align; -- 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