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Message-ID: <45F80FE1.3030603@goop.org>
Date: Wed, 14 Mar 2007 08:08:17 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Lennart Sorensen <lsorense@...lub.uwaterloo.ca>
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>
Subject: Re: Stolen and degraded time and schedulers
Lennart Sorensen wrote:
> How would you deal with something like a pentium 4 HT processor where
> you may run slower just because you got scheduled on the sibling of a
> cpu that happens to run something else needing the same execution units
> you do, causing you to get delayed more, even though the cpu is running
> full speed and nothing else is trying to use your "cpu"? I don't think
> there is any way to know what the real impact of two processes on a HT
> cpu have on each other.
>
> Interesting goal. Not sure it can be done.
You're right. That's a very tough case. I don't know if there's any
way to do a reasonable estimate of the slowdown. You could handwave it
and say "if both threads are running a process, then apply an X scaling
factor to their rate of progress". That might be enough.
J
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