Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933448AbaJVMmS (ORCPT ); Wed, 22 Oct 2014 08:42:18 -0400 Received: from www.linutronix.de ([62.245.132.108]:36454 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933049AbaJVMmR (ORCPT ); Wed, 22 Oct 2014 08:42:17 -0400 Date: Wed, 22 Oct 2014 14:42:09 +0200 (CEST) From: Thomas Gleixner To: Mike Surcouf cc: Thomas Shao , Richard Cochran , Jeff Epler , "gregkh@linuxfoundation.org" , LKML , "devel@linuxdriverproject.org" , "olaf@aepfle.de" , "apw@canonical.com" , "jasowang@redhat.com" , KY Srinivasan , John Stultz , Richard Cochran Subject: Re: [PATCH v2 1/2] timekeeping: add EXPORT_SYMBOL_GPL for do_adjtimex() In-Reply-To: Message-ID: References: <1413362372-16236-1-git-send-email-huishao@microsoft.com> <20141021040212.GA6278@unpythonic.net> <20141021082058.GB6808@netboy> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 22 Oct 2014, Mike Surcouf wrote: > I get that NTP can be installed locally. This is how I regulate time > on my guests. I agree the admin argument probably doesn't stand up. > > The problem is hyperv_clocksource (pluggable time source used by > hyperv guests) is systematically fast in my environment. by around > -250 PPM. > I get away with NTP (just). > However others have had to use tickadj to get hyperv_clocksource close > enough for NTP to work i.e. inside +/-500 PPM. (This IS outside normal > admin tasks) > > So if we are going to use NTP as the solution for hyperv guests (which > is a valid one) the systematic drift of hyperv_clocksource in > different environments will need to be addressed. Maybe this patch > could be modified to tune the tick count on boot before NTP starts and > then leave it alone so NTP can take over. How about fixing hyperv_clocksource in the first place? Thanks, tglx -- 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/