From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751243AbdAQRZm (ORCPT ); Tue, 17 Jan 2017 12:25:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50378 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751162AbdAQRZk (ORCPT ); Tue, 17 Jan 2017 12:25:40 -0500 From: Vitaly Kuznetsov To: Stephen Hemminger Cc: devel@linuxdriverproject.org, Thomas Gleixner , linux-kernel@vger.kernel.org, Haiyang Zhang , "K. Y. Srinivasan" , John Stultz , Alex Ng , Olaf Hering , Richard Cochran Subject: Re: [PATCH v3 0/2] hv_util: adjust system time smoothly References: <20170117152719.23618-1-vkuznets@redhat.com> <20170117083728.7b84feaa@xeon-e3> Date: Tue, 17 Jan 2017 18:15:39 +0100 In-Reply-To: <20170117083728.7b84feaa@xeon-e3> (Stephen Hemminger's message of "Tue, 17 Jan 2017 08:37:28 -0800") Message-ID: <87k29tzjyc.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Tue, 17 Jan 2017 17:15:43 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Stephen Hemminger writes: > On Tue, 17 Jan 2017 16:27:17 +0100 > Vitaly Kuznetsov wrote: > >> With TimeSync version 4 protocol support we started updating system time >> continuously through the whole lifetime of Hyper-V guests. Every 5 seconds >> there is a time sample from the host which triggers do_settimeofday[64](). >> While the time from the host is very accurate such adjustments may cause >> issues: >> - Time is jumping forward and backward, some applications may misbehave. >> - In case an NTP server runs in parallel and uses something else for time >> sync (network, PTP,...) system time will never converge. >> - Systemd starts annoying you by printing "Time has been changed" every 5 >> seconds to the system log. >> >> Instead of doing in-kernel time adjustments offload the work to an >> NTP client by exposing TimeSync messages as a PTP device. Users may now >> decide what they want to use as a source. >> >> Changes since v2: >> - Implement Hyper-V PTP device instead of doint in-kernel time sync. >> >> Changes since "[PATCH RFC] hv_utils: implement Hyper-V PTP source": >> - Richard Cochran: implement .adjfreq, .adjtime, .settime64 returning >> -EOPNOTSUPP. >> - Olaf Hering: change IS_ERR->IS_ERR_OR_NULL as CONFIG_PTP_1588_CLOCK >> can be disabled. >> - Thomas Gleixner: formatting fixes, comments added. >> >> Vitaly Kuznetsov (2): >> hv_util: switch to using timespec64 >> hv_utils: implement Hyper-V PTP source >> >> drivers/hv/hv_util.c | 142 +++++++++++++++++++++++++++++++++++++++++---------- >> 1 file changed, 116 insertions(+), 26 deletions(-) >> > > It would be good to update Documentation files to describe any configuration needed. This is just a PTP device, not any different for other PTP devices so users will be reading their NTP server docs to figure out how to add a PTP reference clock. Or do you have any particular idea where to put an example? -- Vitaly