From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dor Laor Subject: Re: Timedrift in KVM guests after livemigration. Date: Mon, 19 Apr 2010 14:57:42 +0300 Message-ID: <4BCC4536.8010903@redhat.com> References: <4BC6C1B1.5010206@monsternett.no> <4BCA1164.1030808@monsternett.no> <4BCA1756.6060800@msgid.tls.msk.ru> <4BCA4296.2080608@monsternett.no> <4BCACF6E.4010108@redhat.com> <20100418095659.GC4550@redhat.com> <4BCC20AB.3090908@monsternett.no> <20100419092919.GA10744@redhat.com> Reply-To: dlaor@redhat.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Espen Berg , kvm@vger.kernel.org To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:30549 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753710Ab0DSL4W (ORCPT ); Mon, 19 Apr 2010 07:56:22 -0400 In-Reply-To: <20100419092919.GA10744@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 04/19/2010 12:29 PM, Gleb Natapov wrote: > On Mon, Apr 19, 2010 at 11:21:47AM +0200, Espen Berg wrote: >> Den 18.04.2010 11:56, skrev Gleb Natapov: >> >>>> That's two different things here: >>>> The issue that Espen is reporting is that the hosts have different >>>> frequency and guests that relay on the tsc as a source clock will >>>> notice that post migration. The is indeed a problem that -tdf does >>>> not solve. -tdf only adds compensation for the RTC clock emulation. >>>> >>> It's -rtc-td-hack. -tdf does pit compensation, but since usually kernel >>> pit is used it does nothing. >> >> So this "hack" will not solve our problem? As I also stated, in the past the kvmclock MSRs were not sync upon live migration and it was fixed in 1a03675db146dfc760b3b48b3448075189f142cc , better check with the code. >> > If your guest uses RTC for time keeping it may help. Otherwise it does > nothing. > > -- > Gleb. > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html