linux-kernel - Re: [kvm-devel] Réf. : Re: [PATCH 0/4] Virtual Machine Time Accounting

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Message-ID: <5d6222a80708211047x1393524j962afc0a02af5ba3@mail.gmail.com>
Date:	Tue, 21 Aug 2007 14:47:21 -0300
From:	"Glauber de Oliveira Costa" <glommer@...il.com>
To:	"Christian Borntraeger" <borntraeger@...ibm.com>
Cc:	kvm-devel@...ts.sourceforge.net,
	"laurent.vivier@...l.net" <laurent.vivier@...l.net>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"John Stoffel" <john@...ffel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [kvm-devel] Réf. : Re: [PATCH 0/4] Virtual Machine Time Accounting

On 8/21/07, Christian Borntraeger <borntraeger@...ibm.com> wrote:
> Am Montag, 20. August 2007 schrieb Glauber de Oliveira Costa:
> > Although I don't know KVM to a that deep level, I think it should be
> > possible to keep the virtual cpus in different process (or threads),
> > and take the accounting time from there. Perfectly possible to know
> > the time we spent running (user time), and the time the hypervisor
> > spent doing things on our behalf (system time).
>
> I disagree here. First thing, you dont want to have the virtual cpu in a
> different process than the hypervisor control code for that cpu. Otherwise
> communication has to be made via IPC.
> Secondly, Its not qemu/kvm that does the accouting. Its existing userspace
> code like top/snmp agents and clients! etc. that would require additional
> knowledge which thread is guest code.

Yes, the second argument kills me, and I think it leaves no further
room from discussion in my side. Thanks for the enlightenment.

> I personally like the approach Laurent has taken. Maybe it needs some polish
> and maybe we want an account_guest_time function, but in general I think he
> is doing the right thing.
>
Now, me too.

-- 
Glauber de Oliveira Costa.
"Free as in Freedom"
http://glommer.net

"The less confident you are, the more serious you have to act."
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