Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964824AbVKVBbv (ORCPT ); Mon, 21 Nov 2005 20:31:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964826AbVKVBbv (ORCPT ); Mon, 21 Nov 2005 20:31:51 -0500 Received: from mustang.oldcity.dca.net ([216.158.38.3]:24241 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S964824AbVKVBbu (ORCPT ); Mon, 21 Nov 2005 20:31:50 -0500 Subject: Re: test time-warps [was: Re: 2.6.14-rt13] From: Lee Revell To: john stultz Cc: Ingo Molnar , Fernando Lopez-Lezcano , 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: <1132616496.31144.27.camel@cog.beaverton.ibm.com> References: <20051115090827.GA20411@elte.hu> <1132608728.4805.20.camel@cmn3.stanford.edu> <20051121221511.GA7255@elte.hu> <20051121221941.GA11102@elte.hu> <1132616496.31144.27.camel@cog.beaverton.ibm.com> Content-Type: text/plain Date: Mon, 21 Nov 2005 20:31:43 -0500 Message-Id: <1132623104.4772.8.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.4.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 982 Lines: 24 On Mon, 2005-11-21 at 15:41 -0800, john stultz wrote: > I believe this is the same dual-core TSC drift that has been seen w/ > x86-64. I have just added some similar logic to the TSC clocksource > that mimics what x86-64 does so an alternative clocksource will be > selected automatically. > > I should be sending out another release later tonight with these > updates. > It is really unfortunate that the TSC cannot be used for timekeeping on these machines. I wrote a simple benchmark that shows rdtsc on Fernando's box to be insanely fast - 10000 iterations in 68 microseconds. This was an order of magnitude faster than any other machine we tested. Why would they bother making it so fast if it's useless for timekeeping? Lee - 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/