From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andre Przywara Subject: Re: KVM Processor cache size Date: Tue, 3 Aug 2010 00:24:12 +0200 Message-ID: <4C57458C.3090409@amd.com> References: <4C56BF6F.9040402@amd.com> <4C56CCFB.204@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit Cc: Ulrich Drepper , "kvm@vger.kernel.org" To: Ricardo Martins Return-path: Received: from tx2ehsobe004.messaging.microsoft.com ([65.55.88.14]:41519 "EHLO TX2EHSOBE008.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751401Ab0HBWny (ORCPT ); Mon, 2 Aug 2010 18:43:54 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: Ricardo Martins wrote: > Thanks for the answers... > > I am creating an environment with multiple virtual servers, my main > concern is whether I have a noticeable > loss of performance because of this problem, if the answer is yes I > will find another solution for my host server. For server workloads it is less of a concern, that's why this issue hasn't been addressed for such a long time. Usually server workloads are not restricted by cache size or cache access patterns, so you will not notice a slowdown. Please note that QEMU does not restrict the actual cache size of the CPU (which will be fully available to the guest), but only the size _reported_ to the guest. If you are still in doubt, you could do benchmarks with the default CPU model and with -cpu host (maybe even with my patch) to determine whether there is a difference. Regards, Andre. -- Andre Przywara AMD-Operating System Research Center (OSRC), Dresden, Germany Tel: +49 351 488-3567-12