From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v2 3/6] KVM-GST: KVM Steal time accounting Date: Wed, 02 Feb 2011 12:51:17 +0200 Message-ID: <4D493725.402@redhat.com> References: <1296244340-15173-1-git-send-email-glommer@redhat.com> <1296244340-15173-4-git-send-email-glommer@redhat.com> <4D456FF9.2010309@redhat.com> <1296575824.5081.17.camel@mothafucka.localdomain> <4D492DBA.9050603@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, aliguori@us.ibm.com, Rik van Riel , Jeremy Fitzhardinge , Peter Zijlstra To: Glauber Costa Return-path: In-Reply-To: <4D492DBA.9050603@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 02/02/2011 12:11 PM, Avi Kivity wrote: > On 02/01/2011 05:57 PM, Glauber Costa wrote: >> On Sun, 2011-01-30 at 16:04 +0200, Avi Kivity wrote: >> > 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. >> >> Avi, >> >> There are two things here: >> One of them, which is solely the accounting of steal time, (patches 1 to >> 4) has absolutely nothing to do with what you said. Its sole purpose is >> to provide the user with information about "why is my process slow if I >> am using 100 % of my cpu?") > > Right. Like irq and softirq time, we need to report this to the user, > as it's potentially much higher. Of course, it's not enough to just account for this time, you also have to expose it somewhere, and update tools like top(1) to display it. -- error compiling committee.c: too many arguments to function