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Date: Wed, 14 Mar 2007 14:42:56 -0700
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Daniel Walker <dwalker@mvista.com>
CC: john stultz <johnstul@us.ibm.com>, Andi Kleen <ak@suse.de>,
       Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
       Con Kolivas <kernel@kolivas.org>, Rusty Russell <rusty@rustcorp.com.au>,
       Zachary Amsden <zach@vmware.com>, James Morris <jmorris@namei.org>,
       Chris Wright <chrisw@sous-sol.org>,
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       cpufreq@lists.linux.org.uk,
       Virtualization Mailing List <virtualization@lists.osdl.org>,
       Peter Chubb <peterc@gelato.unsw.edu.au>
Subject: Re: Stolen and degraded time and schedulers
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Daniel Walker wrote:
> It's used for measuring execution time, but timers are triggered based
> on that time, so it needs to be actual execution time. I don't know to
> what extent this is already inaccurate on some system tho.
>   

Well, "actual execution time" is a bit ambiguous: should that be "time
actually spent executing", or "time we should have spent executing"?

It looks like cpu_clock_sample() will only return accurate results on
yourself; if you get the sched_ns on a thread on another cpu, it won't
include the time accumulated since the start of its timeslice.

    J