Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262425AbVAZQyp (ORCPT ); Wed, 26 Jan 2005 11:54:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262424AbVAZQxg (ORCPT ); Wed, 26 Jan 2005 11:53:36 -0500 Received: from omx2-ext.sgi.com ([192.48.171.19]:34449 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S262425AbVAZQwG (ORCPT ); Wed, 26 Jan 2005 11:52:06 -0500 Date: Wed, 26 Jan 2005 08:51:15 -0800 (PST) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Benjamin Herrenschmidt cc: john stultz , lkml , Tim Schmielau , George Anzinger , albert@users.sourceforge.net, Ulrich Windl , Dominik Brodowski , David Mosberger , Andi Kleen , Paul Mackerras , schwidefsky@de.ibm.com, keith maanthey , Patricia Gaughen , Chris McDermott , Max Asbock , mahuja@us.ibm.com, Nishanth Aravamudan , Darren Hart , "Darrick J. Wong" , Anton Blanchard Subject: Re: [RFC][PATCH] new timeofday arch specific hooks (v. A2) In-Reply-To: <1106710145.5235.47.camel@gaston> Message-ID: References: <1106607089.30884.10.camel@cog.beaverton.ibm.com> <1106607153.30884.12.camel@cog.beaverton.ibm.com> <1106620134.15850.3.camel@gaston> <1106694561.30884.52.camel@cog.beaverton.ibm.com> <1106697227.5235.28.camel@gaston> <1106698655.1589.8.camel@cog.beaverton.ibm.com> <1106710145.5235.47.camel@gaston> 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 Content-Length: 1649 Lines: 38 On Wed, 26 Jan 2005, Benjamin Herrenschmidt wrote: > On Tue, 2005-01-25 at 16:34 -0800, Christoph Lameter wrote: > > > I just hope that the implementation of one arch does not become a standard > > without sufficient reflection. Could we first get an explanation of > > the rationale of the offsets? From my viewpoint of the ia64 implementation > > I have some difficulty understanding why such complicated things as > > prescale and postscale are necessary in gettimeday and why the simple > > formula that we use in gettimeofday is not sufficient? > > What is complicated here ? The formula, at least as we do on ppc64, is > simply: > > time = (hw_value - prescale offset) / scale + post scale offset Yes that is basically what we do on ia64 but we use different terminology. time = ns_at_last_tick + (hw_value - last_tick_hw_value) * scale >> shift > > What I think is a priority need is some subsystem that manages > > time sources effectively (including the ability of the ntp code to > > scale the appropriately) and does that in an arch independent > > way so that all the code can be consolidated. Extract the best existing > > solutions and work from there. > > Which is what John is trying to do, so help instead of criticizing :) I sure hope that we will be doing that. But so far this has been a new implementation instead otherwise ntp_scale would not be in the gettimeofday function. - 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/