From mboxrd@z Thu Jan  1 00:00:00 1970
From: George Dunlap <George.Dunlap@eu.citrix.com>
Subject: Re: Question about the ability of credit scheduler to
	handle I/O and CPU intensive VMs
Date: Tue, 5 Oct 2010 15:16:52 +0100
Message-ID: <AANLkTintdF5h0-YD6FxjX0dapfbQYdAcK2P-=wHXnBiC@mail.gmail.com>
References: <AANLkTi=Ro24zg-yDPk1+=c0XsZSe2kNn8Gk07Bu4x0WN@mail.gmail.com>
	<AANLkTin9E1m_jFcj4Ak7nB9OxcQynrznpQ_nNPi_U7hN@mail.gmail.com>
	<AANLkTikBWZdpOviSEQSNi_pf66A+zYW8FyQVjiCX8ojm@mail.gmail.com>
	<AANLkTi=Oa0_=vXrr63eALBU2sQa3aLV0NiQHt8hPPvcw@mail.gmail.com>
	<AANLkTimYTbf5meNptCtuiKWfQGd_qSNCkbCNabfREc_0@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Return-path: <xen-devel-bounces@lists.xensource.com>
In-Reply-To: <AANLkTimYTbf5meNptCtuiKWfQGd_qSNCkbCNabfREc_0@mail.gmail.com>
List-Unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xensource.com>
List-Help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-Subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
Sender: xen-devel-bounces@lists.xensource.com
Errors-To: xen-devel-bounces@lists.xensource.com
To: Yuehai Xu <yuehaixu@gmail.com>
Cc: xen-devel@lists.xensource.com, yhxu@wayne.edu
List-Id: xen-devel@lists.xenproject.org

On Tue, Oct 5, 2010 at 3:52 AM, Yuehai Xu <yuehaixu@gmail.com> wrote:
> However, I stop one of the CPU intensive program in a DomU while keep
> the other running, the results are:
> .....
> < =A00.327815345 |x d1v0> (dom: 1) --> (dom: 2) vruntime : 1542607)
> < =A00.327906620 -x d2v0> (dom: 2) --> (dom: 1) vruntime : 109521)
> < =A00.344349033 |x d1v0> (dom: 1) --> (dom: 2) vruntime : 19779544)
> < =A00.344377129 -x d2v0> (dom: 2) --> (dom: 1) vruntime : 33528)
> < =A00.344570662 |x d1v0> (dom: 1) --> (dom: 2) vruntime : 232540)
> < =A00.344643933 -x d2v0> (dom: 2) --> (dom: 1) vruntime : 87857)
> < =A00.345009170 |x d1v0> (dom: 1) --> (dom: 2) vruntime : 439081)
> < =A00.345034387 -x d2v0> (dom: 2) --> (dom: 1) vruntime : 30059)
> < =A00.369973183 -x d1v0> (dom: 1) --> (dom: 1) vruntime : 30000506)
> < =A00.392423279 |x d1v0> (dom: 1) --> (dom: 2) vruntime : 27006658)
> ....
>
> Here I am gotten confusing, since my algorithm of scheduling is very
> simple, every VM should have 30ms of PCPU, however, from the results,
> the time for
> each VCPU to have PCPU is quite unstable. I think somewhere, the
> routine of schedule() should be invoked frequently, and from xentop,
> the VM with CPU
> intensive occupies PCPU almost at 97%.

Idle VMs are never 100% idle; there are a lot of "maintenance" tasks
still to be done.

Your mostly-idle domain (domain 2) seems to be running for pretty
short periods of time -- less than 100us.  That's pretty reasonable.

The question to ask is, what happens when domain 2 wakes up -- is it
put on the runqueue, waiting for the running domain to finish its
timeslice?  Or is it run immediately?  Given the trace you give here,
I would guess that it's run immediately.  If that's not what you
expect, you need to figure out why it's doing that and make it do
something else. :-)

 -George