From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752628AbdA3J3T (ORCPT ); Mon, 30 Jan 2017 04:29:19 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60014 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752011AbdA3J1o (ORCPT ); Mon, 30 Jan 2017 04:27:44 -0500 From: Vitaly Kuznetsov To: KY Srinivasan Cc: "devel\@linuxdriverproject.org" , Thomas Gleixner , "linux-kernel\@vger.kernel.org" , Haiyang Zhang , "John Stultz" , "Alex Ng \(LIS\)" , Stephen Hemminger , Olaf Hering , Richard Cochran , Radim Krcmar Subject: Re: [PATCH v4 2/2] hv_utils: implement Hyper-V PTP source References: <20170119141636.3970-1-vkuznets@redhat.com> <20170119141636.3970-3-vkuznets@redhat.com> Date: Mon, 30 Jan 2017 10:19:51 +0100 In-Reply-To: (KY Srinivasan's message of "Sat, 28 Jan 2017 19:04:55 +0000") Message-ID: <874m0g7vm0.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 [10.5.110.28]); Mon, 30 Jan 2017 09:19:55 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org KY Srinivasan writes: >> -----Original Message----- >> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com] >> Sent: Thursday, January 19, 2017 6:17 AM >> To: devel@linuxdriverproject.org >> Cc: Thomas Gleixner ; linux-kernel@vger.kernel.org; >> Haiyang Zhang ; KY Srinivasan >> ; John Stultz ; Alex Ng (LIS) >> ; Stephen Hemminger >> ; Olaf Hering ; Richard >> Cochran ; Radim Krcmar >> >> Subject: [PATCH v4 2/2] hv_utils: implement Hyper-V PTP source >> >> 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. >> >> I tested the solution with chrony, the config was: >> >> refclock PHC /dev/ptp0 poll 3 precision 1e-9 >> >> The result I'm seeing is accurate enough, the time delta between the guest >> and the host is almost always within [-10us, +10us], the in-kernel solution >> was giving us comparable results. >> >> I also tried implementing PPS device instead of PTP by using not currently >> used Hyper-V synthetic timers (we use only one of four for clockevent) but >> with PPS source only chrony wasn't able to give me the required accuracy, >> the delta often more that 100us. >> >> Signed-off-by: Vitaly Kuznetsov > > Vitaly, > > This patch does not apply. Please rebase and send. > Sure, I'm currently testing v5 which includes the .getcrosststamp() callback support. Will be sending it out shortly. -- Vitaly