From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030206AbVHZTQ2 (ORCPT ); Fri, 26 Aug 2005 15:16:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030207AbVHZTQ2 (ORCPT ); Fri, 26 Aug 2005 15:16:28 -0400 Received: from gateway-1237.mvista.com ([12.44.186.158]:38382 "EHLO av.mvista.com") by vger.kernel.org with ESMTP id S1030206AbVHZTQ2 (ORCPT ); Fri, 26 Aug 2005 15:16:28 -0400 Message-ID: <430F6A7E.203@mvista.com> Date: Fri, 26 Aug 2005 12:16:14 -0700 From: George Anzinger Reply-To: george@mvista.com Organization: MontaVista Software User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.6) Gecko/20050323 Fedora/1.7.6-1.3.2 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Alex Williamson CC: Christoph Lameter , john stultz , linux-kernel@vger.kernel.org Subject: Re: Need better is_better_time_interpolator() algorithm References: <1124988269.5331.49.camel@tdi> <1124991406.20820.188.camel@cog.beaverton.ibm.com> <1124995405.5331.90.camel@tdi> <1125073089.5182.30.camel@tdi> In-Reply-To: <1125073089.5182.30.camel@tdi> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Alex Williamson wrote: > On Fri, 2005-08-26 at 08:39 -0700, Christoph Lameter wrote: > > >>I think a priority is something useful for the interpolators. Some of >>the decisions about which time sources to use also have criteria different >>from drift/latency/jitter/cpu. F.e. timers may not survive various >>power-saving configurations. Thus I would think that we need a priority >>plus some flags. >> >>Some of the criteria for choosing a time source may be: > > > Hi Christoph, > > I sent another followup to this thread with a patch containing a > fairly crude algorithm that I think better explains my starting point. > I'm sure the weighting and scaling factors need work, but I think many > of the criteria you describe will favor the right clock. > > >>1. If a system boots up with a single cpu then there is no question that >>the ITC/TSC should be used because of the fast access. We need to factor in frequency shifting here, especially if it happens with out notice. ~ -- George Anzinger george@mvista.com HRT (High-res-timers): http://sourceforge.net/projects/high-res-timers/