Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756831AbZFKSEl (ORCPT ); Thu, 11 Jun 2009 14:04:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756763AbZFKSEY (ORCPT ); Thu, 11 Jun 2009 14:04:24 -0400 Received: from gir.skynet.ie ([193.1.99.77]:49623 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756758AbZFKSEX (ORCPT ); Thu, 11 Jun 2009 14:04:23 -0400 Date: Thu, 11 Jun 2009 19:04:22 +0100 From: Mel Gorman To: Christoph Lameter Cc: Pekka Enberg , linux-kernel@vger.kernel.org, Larry.Finger@lwfinger.net Subject: Re: [PATCH 2/2] SLUB: Disable debugging if it increases the minimum page order Message-ID: <20090611180422.GJ7302@csn.ul.ie> References: <1244728824.17483.51.camel@penberg-laptop> <1244733119.17483.56.camel@penberg-laptop> <1244734086.17483.59.camel@penberg-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1969 Lines: 50 On Thu, Jun 11, 2009 at 11:49:19AM -0400, Christoph Lameter wrote: > On Thu, 11 Jun 2009, Pekka Enberg wrote: > > > My main point is that a lot of _testers_ will probably enable all SLUB > > debugging by default because we encourage them to and it's pretty bad > > that we end up causing order 1 allocations and oom conditions. > > Other test methods (like PAGE_ALLOC debugging) also have significant side > effects. > True, but they come with huge big warnings and I agree that we don't want to make the SL*B debug warning too drastic, particularly because SL*B debugging is often so valuable and relatively lightweight in comparison to some debug options. > > So I still think we need to fix _at minimum_ the kmalloc-4096 case > > (assuming Larry won't hit the same problem still). I see you're not > > happy with my patch so any suggestions how to handle that? > > Add a warning to Kconfig that the higher order page allocations may > increase with debugging on for caches with object sizes near or equal to > PAGE_SIZE? > Possibly clueless suggestion here. How possible would it be to implement something like "With SLUB_DEBUG, enable debug on all caches unless the increased meta-data would force the minimum order up on order due to object sizes being near or equal the PAGE_SIZE. If SLUB_DEBUG must be enabled, specify slub_debug=A for 'All caches enable debug regardless'" ? > Its good to run with full debugging on for even the 4k sized caches. > Otherwise we wont be catching overruns there. But the debugging can cause > some side effects. > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/