From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1945890AbXC3Cpb (ORCPT ); Thu, 29 Mar 2007 22:45:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1945915AbXC3Cpb (ORCPT ); Thu, 29 Mar 2007 22:45:31 -0400 Received: from x35.xmailserver.org ([64.71.152.41]:45231 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1945890AbXC3Cpa (ORCPT ); Thu, 29 Mar 2007 22:45:30 -0400 X-AuthUser: davidel@xmailserver.org Date: Thu, 29 Mar 2007 19:43:04 -0700 (PDT) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Nick Piggin cc: Ingo Molnar , Nikita Danilov , Linux Kernel Mailing List , Ravikiran G Thirumalai Subject: Re: [rfc][patch] queued spinlocks (i386) In-Reply-To: <20070330015902.GC19407@wotan.suse.de> Message-ID: References: <20070323100418.GA30740@elte.hu> <20070323103243.GE11577@wotan.suse.de> <17925.18904.820106.145029@gargle.gargle.HOWL> <20070324172959.GB542@elte.hu> <20070328064318.GA12508@wotan.suse.de> <20070329013652.GB2390@wotan.suse.de> <20070329071611.GA24176@wotan.suse.de> <20070330015902.GC19407@wotan.suse.de> X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 30 Mar 2007, Nick Piggin wrote: > > I slightly modified it to use cycles: > > > > http://www.xmailserver.org/qspins.c > > Slightly more than slightly ;) > > You want to have a delay _outside_ the critical section as well, for > multi-thread tests, otherwise the releasing CPU often just retakes > the lock (in the unqueued lock case). As I said, most kernel code > should _not_ be dropping and retaking locks. Yeah. ATM it mostly does double-takes. - Davide