From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 2 May 2007 13:45:33 +0100 (BST) From: Hugh Dickins 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 Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: 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, 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