Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753687Ab1BAP7E (ORCPT ); Tue, 1 Feb 2011 10:59:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:16639 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751608Ab1BAP7C (ORCPT ); Tue, 1 Feb 2011 10:59:02 -0500 Subject: Re: [PATCH v2 3/6] KVM-GST: KVM Steal time accounting From: Glauber Costa To: lidong chen Cc: Avi Kivity , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, aliguori@us.ibm.com, Rik van Riel , Jeremy Fitzhardinge , Peter Zijlstra In-Reply-To: References: <1296244340-15173-1-git-send-email-glommer@redhat.com> <1296244340-15173-4-git-send-email-glommer@redhat.com> <4D456FF9.2010309@redhat.com> Content-Type: text/plain; charset="UTF-8" Organization: Red Hat Date: Tue, 01 Feb 2011 13:58:45 -0200 Message-ID: <1296575925.5081.19.camel@mothafucka.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2108 Lines: 52 On Mon, 2011-01-31 at 00:45 +0800, lidong chen wrote: > I think we can use performance counter. > use unhalted core cycles event, in the nmi callback funcation, count > which process is running . > if the vm exit is caused by nmi,discard it. > the system time of qemu process is the time steal by kvm. Performance counters are a scarce resource, so I'd rather not use them, since it will mean forcing a context switch from whoever is using it at the moment. Which is also an expensive operation anyway. So even though it can be possible, in theory, I don't see why use it in this particular case. > > > 2011/1/30 Avi Kivity : > > On 01/28/2011 09:52 PM, Glauber Costa wrote: > >> > >> This patch accounts steal time time in kernel/sched. > >> I kept it from last proposal, because I still see advantages > >> in it: Doing it here will give us easier access from scheduler > >> variables such as the cpu rq. The next patch shows an example of > >> usage for it. > >> > >> Since functions like account_idle_time() can be called from > >> multiple places, not only account_process_tick(), steal time > >> grabbing is repeated in each account function separatedely. > >> > > > > I accept that steal time is worthwhile, but do you have some way to > > demonstrate that the implementation actually works and is beneficial? > > > > Perhaps run two cpu-bound compute processes on one vcpu, overcommit that > > vcpu, and see what happens to the processing rate with and without steal > > time accounting. I'd expect a fairer response with steal time accounting. > > > > -- > > error compiling committee.c: too many arguments to function > > > > -- > > To unsubscribe from this list: send the line "unsubscribe kvm" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/