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From: Dario Faggioli <dario.faggioli@citrix.com>
Subject: Re: memory performance 20% degradation in DomU -- Sisu
Date: Wed, 12 Mar 2014 09:59:30 +0100
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To: Sisu Xi <xisisu@gmail.com>
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On Tue, 2014-03-11 at 10:46 -0500, Sisu Xi wrote:


> Can you be more specific about the highest performance modes of the
> CPU? For all the experiments, I disabled hyperthreading and frequency
> scaling, so CPU should work at a constant speed.
>=20
It was about TurboBoost (or whatever it's called) mode:
 http://en.wikipedia.org/wiki/Intel_Turbo_Boost

Some more info on this old blog post:
 http://blog.xen.org/index.php/2011/11/29/baremetal-vs-xen-vs-kvm-redux/

If you're completely disabling cpufreq via BIOS, I'd say this is ruled
out, but I can't be 100% sure. Also, that should be fixed in recent
enough Xen and Dom0 kernel.

Dario

--=20
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)


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