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

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Message-ID: <18121.39541.790665.686081@stoffel.org>
Date:	Mon, 20 Aug 2007 09:43:17 -0400
From:	"John Stoffel" <john@...ffel.org>
To:	Laurent Vivier <Laurent.Vivier@...l.net>
Cc:	Ingo Molnar <mingo@...e.hu>,
	kvm-devel <kvm-devel@...ts.sourceforge.net>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 0/4] Virtual Machine Time Accounting

Laurent> The aim of these four patches is to introduce Virtual Machine
Laurent> time accounting.

So what does this buy us?  What increased functionality?  

Laurent> [PATCH 1/4] as recent CPUs introduce a third running state,
Laurent> after "user" and "system", we need a new field, "guest", in
Laurent> cpustat to store the time used by the CPU to run virtual
Laurent> CPU. Modify /proc/stat to display this new field.

What happens when you have multiple guests, is this state cummulative?  

I've glanced over these patches and the #ifdefs are ugly..., esp since
the overhead seems to exist even if you don't run any Guest CPUs.  Or
whatever you're doing here.

Please justify this patch more in terms of what it provides and why
it's a good thing to have.  

Thanks,
John
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