Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2993096AbXEBMp7 (ORCPT ); Wed, 2 May 2007 08:45:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S2993097AbXEBMp7 (ORCPT ); Wed, 2 May 2007 08:45:59 -0400 Received: from extu-mxob-2.symantec.com ([216.10.194.135]:64285 "EHLO extu-mxob-2.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2993096AbXEBMp6 (ORCPT ); Wed, 2 May 2007 08:45:58 -0400 Date: Wed, 2 May 2007 13:45:33 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.wat.veritas.com To: Christoph Lameter cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: 2.6.22 -mm merge plans: slub In-Reply-To: Message-ID: References: <20070430162007.ad46e153.akpm@linux-foundation.org> <20070501125559.9ab42896.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-OriginalArrivalTime: 02 May 2007 12:45:57.0039 (UTC) FILETIME=[D43363F0:01C78CB7] X-Brightmail-Verdict: VlJEQwAAAAIAAAABAAAAAAAAAAEAAAAAAAAABGluYm94AGxpbnV4LWtlcm5lbEB2Z2VyLmtlcm5lbC5vcmcAYWtwbUBsaW51eC1mb3VuZGF0aW9uLm9yZwBjbGFtZXRlckBzZ2kuY29tAGxpbnV4LW1tQGt2YWNrLm9yZwA= X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1831 Lines: 41 On Tue, 1 May 2007, Christoph Lameter wrote: > On Tue, 1 May 2007, Hugh Dickins wrote: > > > Yes, to me it does. If it could be defaulted to on throughout the > > -rcs, on every architecture, then I'd say that's "finishing work"; > > and we'd be safe knowing we could go back to slab in a hurry if > > needed. But it hasn't reached that stage yet, I think. > > Why would we need to go back to SLAB if we have not switched to SLUB? SLUB > is marked experimental and not the default. I said above that I thought SLUB ought to be defaulted to on throughout the -rcs: if we don't do that, we're not going to learn much from having it in Linus' tree. And perhaps that line which appends "PREEMPT " to an oops report ought to append "SLUB " too, for so long as there's a choice. > The only problems that I am aware of is(or was) the issue with arches > modifying page struct fields of slab pages that SLUB needs for its own > operations. And I thought it was all fixed since the powerpc guys were > quiet and the patch was in for i386. You're forgetting your unions in struct page: in the SPLIT_PTLOCK case (NR_CPUS >= 4) the pagetable code is using spinlock_t ptl, which overlays SLUB's first_page and slab pointers. I just tried rebuilding powerpc with the SPLIT_PTLOCK cutover edited to 8 cpus instead, and then no crash. I presume the answer is just to extend your quicklist work to powerpc's lowest level of pagetables. The only other architecture which is using kmem_cache for them is arm26, which has "#error SMP is not supported", so won't be giving this problem. Hugh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/