From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: 2.6.22 -mm merge plans: slub on PowerPC From: Benjamin Herrenschmidt In-Reply-To: References: <20070430162007.ad46e153.akpm@linux-foundation.org> <20070501125559.9ab42896.akpm@linux-foundation.org> <20070503011515.0d89082b.akpm@linux-foundation.org> <20070503015729.7496edff.akpm@linux-foundation.org> Content-Type: text/plain Date: Fri, 04 May 2007 10:25:44 +1000 Message-Id: <1178238344.6353.79.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Hugh Dickins Cc: Andrew Morton , Christoph Lameter , Paul Mackerras , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Thu, 2007-05-03 at 22:04 +0100, Hugh Dickins wrote: > On Thu, 3 May 2007, Hugh Dickins wrote: > > > > Seems we're all wrong in thinking Christoph's Kconfiggery worked > > as intended: maybe it just works some of the time. I'm not going > > to hazard a guess as to how to fix it up, will resume looking at > > the powerpc's quicklist potential later. > > Here's the patch I've been testing on G5, with 4k and with 64k pages, > with SLAB and with SLUB. But, though it doesn't crash, the pgd > kmem_cache in the 4k-page SLUB case is revealing SLUB's propensity > for using highorder allocations where SLAB would stick to order 0: > under load, exec's mm_init gets page allocation failure on order 4 > - SLUB's calculate_order may need some retuning. (I'd expect it to > be going for order 3 actually, I'm not sure how order 4 comes about.) > > I don't know how offensive Ben and Paulus may find this patch: > the kmem_cache use was nicely done and this messes it up a little. > > > The SLUB allocator relies on struct page fields first_page and slab, > overwritten by ptl when SPLIT_PTLOCK: so the SLUB allocator cannot then > be used for the lowest level of pagetable pages. This was obstructing > SLUB on PowerPC, which uses kmem_caches for its pagetables. So convert > its pte level to use quicklist pages (whereas pmd, pud and 64k-page pgd > want partpages, so continue to use kmem_caches for pmd, pud and pgd). > But to keep up appearances for pgtable_free, we still need PTE_CACHE_NUM. Interesting... I'll have a look asap. Ben. -- 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