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 mtagate6.de.ibm.com (8.13.7/8.13.7) with ESMTP id k6QAsLQ3111424 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=FAIL) for ; Wed, 26 Jul 2006 10:54:21 GMT Received: from d12av02.megacenter.de.ibm.com (d12av02.megacenter.de.ibm.com [9.149.165.228]) by d12nrmr1607.megacenter.de.ibm.com (8.13.6/NCO/VER7.0) with ESMTP id k6QAvcR2065314 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 26 Jul 2006 12:57:38 +0200 Received: from d12av02.megacenter.de.ibm.com (loopback [127.0.0.1]) by d12av02.megacenter.de.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id k6QAsKo8019084 for ; Wed, 26 Jul 2006 12:54:21 +0200 Date: Wed, 26 Jul 2006 12:52:04 +0200 From: Heiko Carstens Subject: Re: [patch 2/2] slab: always consider arch mandated alignment Message-ID: <20060726105204.GF9592@osiris.boeblingen.de.ibm.com> References: <20060722162607.GA10550@osiris.ibm.com> <20060723073500.GA10556@osiris.ibm.com> <20060723162427.GA10553@osiris.ibm.com> <20060726085113.GD9592@osiris.boeblingen.de.ibm.com> <20060726101340.GE9592@osiris.boeblingen.de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org Return-Path: To: Pekka J Enberg Cc: Christoph Lameter , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Martin Schwidefsky , manfred@colorfullife.com List-ID: On Wed, Jul 26, 2006 at 01:37:42PM +0300, Pekka J Enberg wrote: > On Wed, 26 Jul 2006, Heiko Carstens wrote: > > It's enough to fix the ARCH_SLAB_MINALIGN problem. But it does _not_ fix the > > ARCH_KMALLOC_MINALIGN problem. s390 currently only uses ARCH_KMALLOC_MINALIGN > > since that should be good enough and it doesn't disable as much debugging > > as ARCH_SLAB_MINALIGN does. > > What exactly isn't clear from the description of the first patch? Or why do > > you consider it bogus? > > Now I am confused. What do you mean by "doesn't disable as much debugging > as ARCH_SLAB_MINALIGN does"? AFAICT, the SLAB_RED_ZONE and SLAB_STORE_USER > options _require_ BYTES_PER_WORD alignment, so if s390 requires 8 > byte alignment, you can't have them debugging anyhow... We only specify ARCH_KMALLOC_MINALIGN, since that aligns only the kmalloc caches, but it doesn't disable debugging on other caches that are created via kmem_cache_create() where an alignment of e.g. 0 is specified. The point of the first patch is: why should the slab cache be allowed to chose an aligment that is less than what the caller specified? This does very likely break things. -- 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