From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932489AbXALK6T (ORCPT ); Fri, 12 Jan 2007 05:58:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932666AbXALK6S (ORCPT ); Fri, 12 Jan 2007 05:58:18 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:50637 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932489AbXALK6S (ORCPT ); Fri, 12 Jan 2007 05:58:18 -0500 Date: Fri, 12 Jan 2007 11:19:31 +0100 From: Ingo Molnar To: Avi Kivity Cc: kvm-devel , linux-kernel , Thomas Gleixner Subject: Re: kvm & dyntick Message-ID: <20070112101931.GA11635@elte.hu> References: <45A66106.5030608@qumranet.com> <20070112062006.GA32714@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070112062006.GA32714@elte.hu> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -5.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-5.9 required=5.9 tests=ALL_TRUSTED,BAYES_00 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Ingo Molnar wrote: > > dyntick-enabled guest: > > - reduce the load on the host when the guest is idling > > (currently an idle guest consumes a few percent cpu) > > yeah. KVM under -rt already works with dynticks enabled on both the > host and the guest. (but it's more optimal to use a dedicated > hypercall to set the next guest-interrupt) using the dynticks code from the -rt kernel makes the overhead of an idle guest go down by a factor of 10-15: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2556 mingo 15 0 598m 159m 157m R 1.5 8.0 0:26.20 qemu ( for this to work on my system i have added a 'hyper' clocksource hypercall API for KVM guests to use - this is needed instead of the running-to-slowly TSC. ) Ingo