From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751761AbcESDgb (ORCPT ); Wed, 18 May 2016 23:36:31 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:18184 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750752AbcESDga (ORCPT ); Wed, 18 May 2016 23:36:30 -0400 X-IronPort-AV: E=Sophos;i="5.26,332,1459814400"; d="asc'?scan'208";a="361986273" Message-ID: <1463628977.5851.53.camel@citrix.com> Subject: Re: [Xen-devel] [PATCH] xen: add steal_clock support on x86 From: Dario Faggioli To: Tony S , Boris Ostrovsky , , CC: Juergen Gross , , David Vrabel , George Dunlap Date: Thu, 19 May 2016 05:36:17 +0200 In-Reply-To: References: <1463573758-11441-1-git-send-email-jgross@suse.com> <573C804F.6020708@oracle.com> <573C81D1.9040309@suse.com> <1463587813.5851.35.camel@citrix.com> <573CA455.8060002@oracle.com> Organization: Citrix Inc. Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="=-VIeIC4+40kEiOCaEuEjI" X-Mailer: Evolution 3.18.5.2 (3.18.5.2-1.fc23) MIME-Version: 1.0 X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-VIeIC4+40kEiOCaEuEjI Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2016-05-18 at 12:03 -0600, Tony S wrote: > On Wed, May 18, 2016 at 11:59 AM, Tony S > wrote: > > On Wed, May 18, 2016 at 11:20 AM, Boris Ostrovsky > > wrote: > > > Tony narrowed the problem down to update_curr() where vruntime is > > > calculated, based on runqueue's clock_task value. That value is > > > computed > > > in update_rq_clock_task(), which needs paravirt_steal_rq_enabled. > > >=20 > > Hi Boris, > >=20 > > You are right. > >=20 > > The real problem is steal_clock in pv_time_ops is implemented in > > KVM > > but not in Xen. > >=20 > > [...] > > > > Therefore, even though update_rq_clock_task() calculates the value > > and > > paravirt_steal_rq_enabled option is enabled, the steal value just > > returns 0. This will cause the problem which I mentioned. > >=20 > > update_rq_clock_task > > --> paravirt_steal_clock > > --> pv_time_ops.steal_clock > > --> native_steal_clock (if in Xen) > > --> 0 > >=20 Ok, thanks again for confirming this. > Also, I tried the latest long term version of Linux 4.4, this issue > still exists there. Hoping the next version can add this patch. >=20 Yes, as Juergen said here: =C2=A0http://lists.xen.org/archives/html/xen-devel/2016-05/msg01712.html he has in his plans to implement the full mechanism. It will just take a bit longer, due to the amount of work necessary for this second part. Regards, Dario --=20 <> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) --=-VIeIC4+40kEiOCaEuEjI Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAABCAAGBQJXPTSyAAoJEBZCeImluHPuZX4QAJFlS82OOK1gkNOQx/utSVA+ L2Gfinz1EI7CQyz2zWIZ36es2lMOgP1b/wCcf8AZUhWn/d5I2T3/sRk8S0cW4lJp kW5V09WfbjfQgdApG7phl/K3FV5fCriLb1ZZOuTtnsgP6VExn1WwK67uwLfJBtZP RXIwfaBEWcFl+7FDHDR2G1UVFy4qpRpv1Y5eNEGHbcnvunZg57Yz1soY2EkVh48p xShEg1agX71TOU3v9UTplIlnf0u/ZMVED28TEcBcIQ8s22poWH9i9AxiXXxMkKo8 AW9xbOni6Pkn/pNfw+vnQc1+EdjFcvh96MwWbNiG3JPMtMQzyZxalb49A67mzFWm zxdGvRET4GrX3Ch7QsqxC/odQFtwqQhce9xtq0vk2V+DqxATAVs5Qe7CgLemeeIo 9cmIAf79UQ4zbLmfd842PJ5mZ6RLY04g1MfnS2iV7NaLssQ3Y36KngnJFTdZKFKk cOzJAMF6PxxKYg5vjgJGROQ8sU88Fs1M1+svJlBTPj7OxCkim9H6aWF85evvC+iE K3A3OvLHit6laGEyVEjomFv6xZjSd9a0Zcp0fqc1/ShKvBNSwVssXwmovDf1MDzt VPg55r+BYsyGblHHLcbzFcu4CDGkLxawzgEi0+SjmnigrTLo2cw2SeOZZao+FwS4 c5zwHWQd4g3a1N10aGYj =ob64 -----END PGP SIGNATURE----- --=-VIeIC4+40kEiOCaEuEjI--