From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: Performance issue Date: Sun, 25 Nov 2012 17:19:50 +0200 Message-ID: <20121125151949.GD25516@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: kvm@vger.kernel.org To: George-Cristian =?utf-8?Q?B=C3=AErzan?= Return-path: Received: from mx1.redhat.com ([209.132.183.28]:46650 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752712Ab2KYPTw convert rfc822-to-8bit (ORCPT ); Sun, 25 Nov 2012 10:19:52 -0500 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Nov 22, 2012 at 09:17:34PM +0200, George-Cristian B=C3=AErzan w= rote: > I'm trying to understand a performance problem (50% degradation in th= e > VM) that I'm experiencing some systems with qemu-kvm. Running Fedora > with 3.5.3-1.fc17.x86_64 or 3.6.6-1.fc17.x86_64, qemu 1.0.1 or 1.2.1 > on AMD Opteron 6176 and 6174, and all of them behave identically. >=20 > A Windows guest is receiving a UDP MPEG stream that is being processe= d > by TSReader. The stream comes in at about 73Mbps, but the VM cannot > process more than 43Mbps. It's not a networking issue, the packets > reach the guest and with iperf we can easily do 80Mbps. Also, with > iperf, it can receive the packets from the streamer (even though it > doesn't detect things properly, but it was just a way to see ). >=20 > However, on an identical host (a 6174 CPU, even), a Windows install > has absolutely no problem processing the same stream. >=20 What Windows is this? Can you try changing "-cpu host" to "-cpu host,+hv_relaxed"? -- Gleb.