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 12:11:06 +0200 Message-ID: <4D492DBA.9050603@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> 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: <1296575824.5081.17.camel@mothafucka.localdomain> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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. > The last patch is the only one that actually tries to rebalance cpus > according to steal time information. For that, I do have some > experiments I did here to see if it is working, will try to provide more > precise data in the next submission. > Thanks. -- error compiling committee.c: too many arguments to function