Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750701AbWIFIsl (ORCPT ); Wed, 6 Sep 2006 04:48:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750702AbWIFIsl (ORCPT ); Wed, 6 Sep 2006 04:48:41 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:23983 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1750701AbWIFIsk (ORCPT ); Wed, 6 Sep 2006 04:48:40 -0400 Date: Wed, 6 Sep 2006 10:40:21 +0200 From: Ingo Molnar To: Hua Zhong Cc: "'Heiko Carstens'" , "'Andrew Morton'" , linux-kernel@vger.kernel.org, "'Arjan van de Ven'" , "'Daniel Walker'" Subject: Re: lockdep oddity Message-ID: <20060906084021.GA30856@elte.hu> References: <20060906080129.GD6898@osiris.boeblingen.de.ibm.com> <004901c6d18d$acc45620$0200a8c0@nuitysystems.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <004901c6d18d$acc45620$0200a8c0@nuitysystems.com> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -2.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.9 required=5.9 tests=ALL_TRUSTED,AWL,BAYES_50 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts 0.5 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.4932] -0.1 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 751 Lines: 21 * Hua Zhong wrote: > We are just trading accuracy for speed here. no, we are trading _both_ accuracy and speed here! a global 'likeliness' pointer for commonly executed codepaths is causing global cacheline ping-pongs - which is as bad as it gets. the right approach, which incidentally would also be perfectly accurate, is to store an alloc_percpu()-ed pointer at the call site, not the counter itself. the current code needs more work before it can go upstream i think. Ingo - 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/