From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: Lost of performance over AMD-V with KVM? Date: Tue, 9 Jul 2013 17:47:22 +0300 Message-ID: <20130709144722.GD24941@redhat.com> References: <51DC001B.2010703@usc.es> <20130709133340.GA24941@redhat.com> <51DC1EC4.4000001@usc.es> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kvm@vger.kernel.org To: Victor fernandez Return-path: Received: from mx1.redhat.com ([209.132.183.28]:18185 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753512Ab3GIOr1 convert rfc822-to-8bit (ORCPT ); Tue, 9 Jul 2013 10:47:27 -0400 Content-Disposition: inline In-Reply-To: <51DC1EC4.4000001@usc.es> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Jul 09, 2013 at 04:31:32PM +0200, Victor fernandez wrote: > Hi Gleb, >=20 > there are flags that with the tuning of KVM (-cpu host) we get > that some of > important cpu flags are not included in SL6 ( Ht, rdtscp, > 3dnowext, 3dnow, > constant_tsc,nonstop_tsc,amd_dcm,monitor,svm,extapic,osvw,ibs,skinit,= wdt,nodeid_msr). >=20 Not all of them will be passed to a guest even with -cpu host, but instruction set related once like 3dnowext/3dnow you should be. What is qemu command line that you use?=20 > And the machines used for testing were 2 nodes AMD 6128 - 2Ghz - > 2 CPUs > (8 Cores/CPU Core - 1GB) 16 Cores Total - 16 GB RAM for AMD-V > virtualization, > and we did the same tests with the same software versions with 2 > nodes of DELL > PowerEdge SC1950, biprocessors dual core, 2 Xeon(R) CPU 5160 @ > 3.00GHz, > 16GB RAM. for Intel VT virtualization. And with Intel technology > we get the > typical virtualization performance, around 2-5% of lost. >=20 > Thanks in advance, > V=C3=ADctor Fdez. >=20 > El 09/07/13 15:33, Gleb Natapov escribi=C3=B3: > >On Tue, Jul 09, 2013 at 02:20:43PM +0200, Victor fernandez wrote: > >>Hi EveryBody! > >> > >>recently, we have tested some specific High Energy Physics benchmar= ks that > >>was running over S.L.6 and we observed that the performance over AM= D > >>machines was really bad, about 30-40% lost. We were investigating > >>and we conclude that the problem was with some cpu flags. These cpu > >>flags are important for running our application because it is optim= azed > >>for running with them. So, we tuning our KVM with the name of flags > >>parameters and with "-cpu host" parameter too, but > >>we observed that the flags that we needed, they weren't included wh= en > >>we started the S.L.6 instance. We try to solve it, but when we conc= lude > >>that the specific flags weren't included in the code of the last > >>versions of KVM > >>and LibVirt(capabilities). Do you know something about this problem= or > >>you are aware of this? > >> > >What flags are missing? > > > >-- > > Gleb. >=20 -- Gleb.