Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761228AbZANLWv (ORCPT ); Wed, 14 Jan 2009 06:22:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753871AbZANLWe (ORCPT ); Wed, 14 Jan 2009 06:22:34 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:41999 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753302AbZANLWd (ORCPT ); Wed, 14 Jan 2009 06:22:33 -0500 Date: Wed, 14 Jan 2009 12:21:58 +0100 From: Ingo Molnar To: Chris Mason Cc: Peter Zijlstra , Linus Torvalds , "Paul E. McKenney" , Gregory Haskins , Matthew Wilcox , Andi Kleen , Andrew Morton , Linux Kernel Mailing List , linux-fsdevel , linux-btrfs , Thomas Gleixner , Nick Piggin , Peter Morreale , Sven Dietrich , Dmitry Adamushko Subject: Re: [PATCH -v9][RFC] mutex: implement adaptive spinning Message-ID: <20090114112158.GA8625@elte.hu> References: <1231774622.4371.96.camel@laptop> <1231859742.442.128.camel@twins> <1231863710.7141.3.camel@twins> <1231864854.7141.8.camel@twins> <1231867314.7141.16.camel@twins> <1231901899.1709.18.camel@think.oraclecorp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1231901899.1709.18.camel@think.oraclecorp.com> User-Agent: Mutt/1.5.18 (2008-05-17) 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 Content-Length: 985 Lines: 29 * Chris Mason wrote: > v10 is better that not spinning, but its in the 5-10% range. So, I've > been trying to find ways to close the gap, just to understand exactly > where it is different. > > If I take out: > /* > * If there are pending waiters, join them. > */ > if (!list_empty(&lock->wait_list)) > break; > > > v10 pops dbench 50 up to 1800MB/s. The other tests soundly beat my > spinning and aren't less fair. But clearly this isn't a good solution. i think since we already decided that it's ok to be somewhat unfair (_all_ batching constructs introduce unfairness, so the question is never 'should we?' but 'by how much?'), we should just take this out and enjoy the speed ... 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/