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

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Date:	Mon, 20 Aug 2007 19:54:52 +0200
From:	laurent.vivier@...l.net
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	John Stoffel <john@...ffel.org>,
	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	Laurent Vivier <Laurent.Vivier@...l.net>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	virtualization <virtualization@...ts.linux-foundation.org>
Subject: Réf. : Re: [PATCH 0/4] Virtual Machine Time
 Accounting


> Laurent Vivier wrote:
> functionnalities:
>
> > - allow to measure time spent by a CPU in a virtual CPU.
> > - allow to display in /proc/state this value by CPU
> > - allow to display in /proc/<pid>/state this value by process
> > - allow KVM to use these 3 previous functionnalities
> >
>
> So, currently time spent in a kvm guest is accumulated as qemu-kvm
> usertime, right?  Given that qemu knows when its running in qemu vs

No, it is accumulated as kvm system time.

> guest context, couldn't it provide the breakdown between user and guest
> time (ditto lguest)?

by doing this at kernel level, we can:
- measure exactly the guest time,
- move this part of system time to user time (as you think it should be
user time),
- have consistency between system, user and guest time,
- report values in /proc/state and /proc/<pid>/state, at system wide level

I'm not sure we can measure the guest time at the qemu user level.

Perhaps Rusty can say what he thinks about this ?

Regards,
Laurent


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