From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 26 Jul 2006 11:59:57 -0700 (PDT) From: Christoph Lameter Subject: Re: [patch 2/2] slab: always consider arch mandated alignment In-Reply-To: <44C7B842.5060606@colorfullife.com> Message-ID: 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> <20060726105204.GF9592@osiris.boeblingen.de.ibm.com> <44C7AF31.9000507@colorfullife.com> <44C7B842.5060606@colorfullife.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Manfred Spraul Cc: Pekka J Enberg , Heiko Carstens , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Martin Schwidefsky List-ID: On Wed, 26 Jul 2006, Manfred Spraul wrote: > > Thus the patch is correct, it's a bug in the slab allocator. If > > HWCACHE_ALIGN > > > is set, then the allocator ignores align or ARCH_SLAB_MINALIGN. > > > > > > But then Heiko does not want to set ARCH_SLAB_MINALIGN at all. This is not > > the issue we are discussing. In the DEBUG case he wants > > ARCH_KMALLOC_MINALIGN to be enforced even if ARCH_SLAB_MINALIGN is not set. > > > The kmalloc caches are allocated with HWCACHE_ALIGN+ARCH_KMALLOC_MINALIGN. The > logic in kmem_cache_create didn't handle that case correctly. > On most architectures, ARCH_KMALLOC_MINALIGN is 0. Thus SLAB_DEBUG redzones > everything. > On s390, ARCH_KMALLOC_MINALIGN is 8. This disables redzoning. > > Ok? So Redzoning etc will now be diabled regardless even if ARCH_SLAB_MINALIGN is not set but another alignment is given to kmem_cache_alloc? So we sacrifice the ability to worsen the performance of slabs by misaligning them for debugging purposes. -- 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