From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: Why do additional cores reduce performance? Date: Tue, 16 Dec 2014 17:31:13 +0100 Message-ID: <54905E51.10600@redhat.com> References: <548FFAAD.5040601@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: qemu-discuss@nongnu.org, kvm@vger.kernel.org To: Oleg Ovechko Return-path: Received: from mail-wg0-f46.google.com ([74.125.82.46]:34730 "EHLO mail-wg0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750873AbaLPQbS (ORCPT ); Tue, 16 Dec 2014 11:31:18 -0500 Received: by mail-wg0-f46.google.com with SMTP id x13so18067977wgg.33 for ; Tue, 16 Dec 2014 08:31:17 -0800 (PST) In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On 16/12/2014 17:22, Oleg Ovechko wrote: >> What is your benchmark? > > I've tried different ways (CrystalDiskMark 3.0.3 x64, ATTO Disk > Banchmark v2.47) all give same result. All are run on the AHCI passthrough disk(s), right? > When everything is enabled in BIOS it is 6:23 on real Windows versus > 9:03 on virtualized... > > Phil Ehrens has sent me link > https://lists.gnu.org/archive/html/qemu-discuss/2014-10/msg00036.html > If I don't misunderstand, it means kvm/qemu simply is not designed for > multi-threading. No, it means TCG does not support multithreading. KVM does, and you are using it. > I guess I need to try different hypervisor. 50% performance is too > high price especially when VT-x and VT-d are meant to make it 0% It is surprising to me too. Paolo