Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752726AbXJAVcS (ORCPT ); Mon, 1 Oct 2007 17:32:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752588AbXJAVcC (ORCPT ); Mon, 1 Oct 2007 17:32:02 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:34922 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752628AbXJAVcA (ORCPT ); Mon, 1 Oct 2007 17:32:00 -0400 Date: Mon, 1 Oct 2007 14:30:47 -0700 From: Andrew Morton To: Christoph Lameter Cc: a.p.zijlstra@chello.nl, nickpiggin@yahoo.com.au, hch@lst.de, mel@skynet.ie, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, dgc@sgi.com, jens.axboe@oracle.com Subject: Re: [15/17] SLUB: Support virtual fallback via SLAB_VFALLBACK Message-Id: <20071001143047.238dfe49.akpm@linux-foundation.org> In-Reply-To: References: <20070919033605.785839297@sgi.com> <20070919033643.763818012@sgi.com> <200709280742.38262.nickpiggin@yahoo.com.au> <1191002119.18147.80.camel@lappy> <1191003950.18147.85.camel@lappy> <20070929011311.8b51dedb.akpm@linux-foundation.org> <1191055632.18147.101.camel@lappy> <20070929020049.f73f4aea.akpm@linux-foundation.org> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1808 Lines: 46 On Mon, 1 Oct 2007 13:55:29 -0700 (PDT) Christoph Lameter wrote: > On Sat, 29 Sep 2007, Andrew Morton wrote: > > > > atomic allocations. And with SLUB using higher order pages, atomic !0 > > > order allocations will be very very common. > > > > Oh OK. > > > > I thought we'd already fixed slub so that it didn't do that. Maybe that > > fix is in -mm but I don't think so. > > > > Trying to do atomic order-1 allocations on behalf of arbitray slab caches > > just won't fly - this is a significant degradation in kernel reliability, > > as you've very easily demonstrated. > > Ummm... SLAB also does order 1 allocations. We have always done them. > > See mm/slab.c > > /* > * Do not go above this order unless 0 objects fit into the slab. > */ > #define BREAK_GFP_ORDER_HI 1 > #define BREAK_GFP_ORDER_LO 0 > static int slab_break_gfp_order = BREAK_GFP_ORDER_LO; Do slab and slub use the same underlying page size for each slab? Single data point: the CONFIG_SLAB boxes which I have access to here are using order-0 for radix_tree_node, so they won't be failing in the way in which Peter's machine is. I've never ever before seen reports of page allocation failures in the radix-tree node allocation code, and that's the bottom line. This is just a drop-dead must-fix show-stopping bug. We cannot rely upon atomic order-1 allocations succeeding so we cannot use them for radix-tree nodes. Nor for lots of other things which we have no chance of identifying. Peter, is this bug -mm only, or is 2.6.23 similarly failing? - 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/