linux-kernel - Re: Stolen and degraded time and schedulers

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Message-ID: <45F8516E.0@goop.org>
Date:	Wed, 14 Mar 2007 12:47:58 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Rik van Riel <riel@...hat.com>
CC:	Dan Hecht <dhecht@...are.com>, dwalker@...sta.com,
	cpufreq@...ts.linux.org.uk,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Con Kolivas <kernel@...ivas.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	john stultz <johnstul@...ibm.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>, paulus@...ibm.com,
	schwidefsky@...ibm.com
Subject: Re: Stolen and degraded time and schedulers

Rik van Riel wrote:
> Jeremy Fitzhardinge wrote:
>
>> It doesn't matter why you didn't get the time; 
>
> Oh, but it does.

I meant specifically from a scheduling perspective.

> System administrators can use steal time the same way they
> use iowait time: to spot bottlenecks on their systems.
>
> If you have a lot of iowait time, you know you want either
> faster IO or more memory.
>
> If you have a lot of steal time, you know you need to spread
> your virtual machines over more CPUs.
>
> Steal time allows you to see the difference between a busy
> system and an overloaded system.

Sure, the various accounting tools can go into as much detail as you
want.  I just added stolen time accounting to the xen-pv_ops patchset
which is equivalent to the xen-unstable stolen time accounting.  Is that
sufficient for these purposes?

    J
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