From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA46EC6786F for ; Thu, 1 Nov 2018 17:45:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A123220657 for ; Thu, 1 Nov 2018 17:45:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A123220657 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728032AbeKBCtL (ORCPT ); Thu, 1 Nov 2018 22:49:11 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:57877 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726085AbeKBCtL (ORCPT ); Thu, 1 Nov 2018 22:49:11 -0400 Received: from p5492fe24.dip0.t-ipconnect.de ([84.146.254.36] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1gIH1e-0007sg-9T; Thu, 01 Nov 2018 18:44:58 +0100 Date: Thu, 1 Nov 2018 18:44:57 +0100 (CET) From: Thomas Gleixner To: John Stultz cc: Christopher Hall , "H. Peter Anvin" , linux-rt-users , jesus.sanchez-palencia@intel.com, Gavin Hindman , liam.r.girdwood@intel.com, Peter Zijlstra , LKML , Miroslav Lichvar Subject: Re: TSC to Mono-raw Drift In-Reply-To: Message-ID: References: <20181015160945.5993-1-christopher.s.hall@intel.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 23 Oct 2018, John Stultz wrote: > On Fri, Oct 19, 2018 at 3:36 PM, John Stultz wrote: > I spent a little bit of time thinking this out. Unfortunately I don't > think its a simple matter of calculating the granularity error on the > raw clock and adding it in each interval. The other trouble spot is > that the adjusted clocks (monotonic/realtime) are adjusted off of that > raw clock. So they would need to have that error added as well, > otherwise the raw and a otherwise non-adjusted monotonic clock would > drift. > > However, to be correct, the ntp adjustments made would have to be made > to both the base interval + error, which mucks the math up a fair bit. Hmm, confused as usual. Why would you need to do anything like that? Thanks, tglx