Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932081AbVKRWGi (ORCPT ); Fri, 18 Nov 2005 17:06:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932120AbVKRWGi (ORCPT ); Fri, 18 Nov 2005 17:06:38 -0500 Received: from smtp2.Stanford.EDU ([171.67.16.125]:54944 "EHLO smtp2.Stanford.EDU") by vger.kernel.org with ESMTP id S932081AbVKRWGh (ORCPT ); Fri, 18 Nov 2005 17:06:37 -0500 Subject: Re: 2.6.14-rt13 From: Fernando Lopez-Lezcano To: Lee Revell Cc: nando@ccrma.Stanford.EDU, Ingo Molnar , linux-kernel@vger.kernel.org, "Paul E. McKenney" , "K.R. Foley" , Steven Rostedt , Thomas Gleixner , pluto@agmk.net, john cooper , Benedikt Spranger , Daniel Walker , Tom Rini , George Anzinger In-Reply-To: <1132350882.6874.23.camel@mindpipe> References: <20051115090827.GA20411@elte.hu> <1132336954.20672.11.camel@cmn3.stanford.edu> <1132350882.6874.23.camel@mindpipe> Content-Type: text/plain Date: Fri, 18 Nov 2005 14:05:33 -0800 Message-Id: <1132351533.4735.37.camel@cmn3.stanford.edu> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1340 Lines: 30 On Fri, 2005-11-18 at 16:54 -0500, Lee Revell wrote: > On Fri, 2005-11-18 at 10:02 -0800, Fernando Lopez-Lezcano wrote: > > You mentioned before that the TSC's from both cpus could drift from > > each other over time. Assuming that is the source of timing (I have no > > idea) that could explain the behavior of Jack, it gets a reference > > time from one of the cpus and then compares that with what it gets > > from either cpu depending on where it is running at a given time. If > > it is the same cpu all is fine, if it is the other and it has drifted > > then the warning is printed. > > Yes, JACK uses rdtsc() for microsecond resolution timing and assumes > that the TSCs are in sync. > > I've asked on this list what a better time source could be and didn't > get any useful responses, people just told me "use gettimeofday()" which > is WAY too slow. Arghhh, at least I take this as a confirmation that the TSCs do drift and there is no workaround. It currently makes the -rt/Jack combination not very useful, at least in my tests. Is there a way to resync the TSCs? -- Fernando - 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/