From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751314Ab1ADXi5 (ORCPT ); Tue, 4 Jan 2011 18:38:57 -0500 Received: from ms01.sssup.it ([193.205.80.99]:59347 "EHLO sssup.it" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751257Ab1ADXiz (ORCPT ); Tue, 4 Jan 2011 18:38:55 -0500 Message-ID: <4D23AF8A.6080306@sssup.it> Date: Wed, 05 Jan 2011 00:38:50 +0100 From: Tommaso Cucinotta User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101208 Thunderbird/3.1.7 MIME-Version: 1.0 To: Peter Zijlstra , a.p.zijlstra@chello.nl CC: Dario Faggioli , Dhaval Giani , Fabio Checconi , riel@redhat.com, Hillf Danton , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Avi Kiviti , Srivatsa Vaddagiri , Mike Galbraith , Chris Wright Subject: Re: [Fwd: Re: [RFC -v3 PATCH 2/3] sched: add yield_to function] References: <1294164920.6169.199.camel@Palantir> In-Reply-To: <1294164920.6169.199.camel@Palantir> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 04/01/2011 19:15, Dario Faggioli ha scritto: > > -------- Forwarded Message -------- > From: Peter Zijlstra > To: Rik van Riel > Cc: Hillf Danton,kvm@vger.kernel.org, > linux-kernel@vger.kernel.org, Avi Kiviti, Srivatsa > Vaddagiri, Mike Galbraith, > Chris Wright > Subject: Re: [RFC -v3 PATCH 2/3] sched: add yield_to function > Date: Tue, 04 Jan 2011 19:05:54 +0100 > RT guests don't make sense, there's nowhere near enough infrastructure > for that to work well. > > I'd argue that KVM running with RT priority is a bug. Peter, can I ask why did you state that ? In the IRMOS project, we are just deploying KVM VMs by using the Fabio's real-time scheduler (for others, a.k.a., the Fabio's EDF throttling patch, or IRMOS RT scheduler) in order to let the VMs get precise CPU scheduling guarantees by the kernel. So, in this context we do have KVM running at RT priority, and we do have experimental results showing how this can improve stability of performance of the hosted guest VMs. Of course, don't misunderstand me: this is a necessary condition for a stable performance of KVM VMs, I'm not saying it is sufficient for -- Tommaso Cucinotta, Computer Engineering PhD, Researcher ReTiS Lab, Scuola Superiore Sant'Anna, Pisa, Italy Tel +39 050 882 024, Fax +39 050 882 003 http://retis.sssup.it/people/tommaso