Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932092AbYB0XeS (ORCPT ); Wed, 27 Feb 2008 18:34:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751511AbYB0XeI (ORCPT ); Wed, 27 Feb 2008 18:34:08 -0500 Received: from relay1.sgi.com ([192.48.171.29]:38965 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750964AbYB0XeH (ORCPT ); Wed, 27 Feb 2008 18:34:07 -0500 Date: Wed, 27 Feb 2008 15:34:07 -0800 (PST) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Mathieu Desnoyers cc: Eric Dumazet , Pekka Enberg , Torsten Kaiser , Ingo Molnar , Linus Torvalds , Linux Kernel Mailing List Subject: Re: Linux 2.6.25-rc2 In-Reply-To: <20080219200358.GB11197@Krystal> Message-ID: References: <64bb37e0802161338j306c1357m25bc224f09e6b7cd@mail.gmail.com> <20080219061107.GA23229@elte.hu> <64bb37e0802182254l49b10cbblc23f8a83d189ff8e@mail.gmail.com> <84144f020802182321x452888bai639c71ea2a5067da@mail.gmail.com> <20080219140230.GA32236@Krystal> <20080219172739.55c341b5.dada1@cosmosbay.com> <20080219200358.GB11197@Krystal> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1111 Lines: 22 On Tue, 19 Feb 2008, Mathieu Desnoyers wrote: > I think you are right. A way to fix this would use the fact that the > freelist is only useful to point to the first free object in a page. We > could change it to an offset rather than an address. > > The freelist would become a counter of type "long" which increments > until it wraps at 2^32 or 2^64. A PAGE_MASK bitmask could then be used > to get low order bits which would get the page offset of the first free > object, while the high order bits would insure we can detect this type > of object reuse when doing a cmpxchg. Upon free, the freelist counter > should always be incremented; this would be provided by adding PAGE_SIZE > to the counter and setting the LSBs to the correct offset. Urgh.... That sounds way too complicated. Do you have an experimental patch that would allow us to see the impact? -- 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/