From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753778AbbAGQ5e (ORCPT ); Wed, 7 Jan 2015 11:57:34 -0500 Received: from mail.emea.novell.com ([130.57.118.101]:35107 "EHLO mail.emea.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753544AbbAGQ5d convert rfc822-to-8bit (ORCPT ); Wed, 7 Jan 2015 11:57:33 -0500 Message-Id: <54AD7387020000780005271C@mail.emea.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.0.1 Date: Wed, 07 Jan 2015 16:57:27 +0000 From: "Jan Beulich" To: "Ian Campbell" , "Imre Palik" Cc: "Anthony Liguori" , "Imre Palik" , "David Vrabel" , , "Thomas Gleixner" , , "Boris Ostrovsky" , "Ingo Molnar" , , "H. Peter Anvin" Subject: Re: [Xen-devel] [PATCH RFC] xen-time: decreasing the rating of the xen clocksource below that of the tsc clocksource for dom0's References: <1420647398-20207-1-git-send-email-imrep.amz@gmail.com> <1420648234.18631.117.camel@citrix.com> In-Reply-To: <1420648234.18631.117.camel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> On 07.01.15 at 17:30, wrote: > On Wed, 2015-01-07 at 17:16 +0100, Imre Palik wrote: >> From: "Palik, Imre" >> >> In Dom0's the use of the TSC clocksource (whenever it is stable enough to >> be used) instead of the Xen clocksource should not cause any issues, as >> Dom0 VMs never live-migrated. > > Is this still true given that dom0's vcpus are migrated amongst pcpus on > the host? The tsc are not synchronised on some generations of hardware > so the result there would be the TSC appearing to do very odd things > under dom0's feet. Does Linux cope with that or does it not matter for > some other reason? Indeed. The textual qualification above ("whenever it is stable enough") isn't being expressed in the code change at all. Jan