From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935985AbYDQKGP (ORCPT ); Thu, 17 Apr 2008 06:06:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934949AbYDQJqZ (ORCPT ); Thu, 17 Apr 2008 05:46:25 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:36559 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934726AbYDQJqV (ORCPT ); Thu, 17 Apr 2008 05:46:21 -0400 Date: Thu, 17 Apr 2008 11:46:06 +0200 From: Ingo Molnar To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Thomas Gleixner , "H. Peter Anvin" Subject: Re: [v2.6.26] what's brewing in x86.git for v2.6.26 Message-ID: <20080417094606.GA19607@elte.hu> References: <20080416202338.GA6007@elte.hu> <20080417002552.5742ad65.akpm@linux-foundation.org> <20080417083000.GA4935@elte.hu> <20080417014054.ea788f1f.akpm@linux-foundation.org> <20080417090626.GA14383@elte.hu> <20080417021813.04df7912.akpm@linux-foundation.org> <20080417093025.GA17389@elte.hu> <20080417023603.672d1032.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080417023603.672d1032.akpm@linux-foundation.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Morton wrote: > > you mean kmemcheck? Yes, that's planned. We've been working 4 months > > non-stop on kmemcheck to make it mergeable and usable, it's at > > version 7 right now, and it caught a handful of real bugs already > > (such as 63a7138671c - unfortunately not credited in the log to > > kmemcheck). But because it touches SLUB (because it has to - and > > they are acked by Pekka) i never had the chance to move it into the > > for-akpm branch. > > Does it really really really need to consume one of our few remaining > page flags? We'll be in a mess when we run out. well AFAICS the shortage really mostly affects 32-bit platforms. And there we've got 19 bits used, out of 23 available, right? whether we track a page or not is rather fundamental to kmemcheck, i dont see any easy way to get rid of that usage. (and since kmemcheck is a transparent add-on, i dont see any obvious other candidate like page->private either - all those fields might be utilized) if we run out of that in the future: the high bits get used by sparse section and numa node ID bits, worst-case we could live with restricting the max number of NUMA nodes on 32-bit from 64 to 32? [NUMA on 32-bit is an afterthought anyway.] Or we could do a CONFIG_KMEMCHECK=y only page->flags_debug. Ingo