From mboxrd@z Thu Jan 1 00:00:00 1970 From: Riccardo Brunetti Subject: CPU Overcommitting question Date: Fri, 18 Jul 2014 15:06:59 +0200 Message-ID: <53C91BF3.6030507@dnshosting.it> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from mail1.colt-engine.it ([81.31.145.233]:40397 "EHLO mail.colt-engine.it" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965779AbaGRNPF (ORCPT ); Fri, 18 Jul 2014 09:15:05 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.colt-engine.it (Postfix) with ESMTP id 526809FA for ; Fri, 18 Jul 2014 15:07:01 +0200 (CEST) Received: from localhost.localdomain (unknown [81.31.144.178]) by mail.colt-engine.it (Postfix) with ESMTPSA id 89B9A9B3 for ; Fri, 18 Jul 2014 15:06:59 +0200 (CEST) Sender: kvm-owner@vger.kernel.org List-ID: Dear KVM community people, we are running on a kvm hypervisor with the following configuration: CPU : Dual socket 6 cores: Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20GHz RAM : 48 GB OS: CentOS release 6.5 2 very cpu intensive virtual machines and we are trying to find the best way to optimize the available resources. In particular what we would like to understand is how many vCPUs can be assigned to each VM, in order to possibly exploit the overcommitting features of the virtualization without degrading the performances. The first question is about hyperthreading: should it be enabled and the virtual cores be considered? The second quesion is about the way to assign vCPUs between the two VMs. Let's suppose we do not enable the hyperthreading, in our understanding we have the following options: 1) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) = total number of physical cores (12) (both VMs have < 12 vCPUs) (ie. 8+4) 2) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) > total number of physical cores (12) (both VMs have <= 12 vCPUs) (ie. 12+8) 3) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) > total number of physical cores (12) (one VM has > 12 vCPUs) (ie. 16+8) 4) Assign vCPUs so that vCPU(VM1) + vCPU(VM2) > total number of physical cores (12) (both VMs have > 12 vCPUs) (ie. 16+16) According to your experience which would be the best one? Thank you very much. Kind Regards. B. Riccardo