From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <juergen.gross@ts.fujitsu.com>
Subject: Re: CAP and performance problem
Date: Thu, 06 Jun 2013 12:39:08 +0200
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To: Massimo Canonico <mex@di.unipmn.it>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>, Dario Faggioli <dario.faggioli@citrix.com>, xen-devel@lists.xen.org
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On 06.06.2013 10:57, Massimo Canonico wrote:
>
> On 06/06/2013 10:37 AM, Dario Faggioli wrote:
>> On mer, 2013-06-05 at 19:05 +0200, Massimo Canonico wrote:
>>> Hi Dario,
>>> and thanks for these test.
>>>
>>> I forgot to ask you which xen version has beed used for your experiments.
>>>
>> Yeah, me too! :-)
>>
>> I'm using xen-unstable, pulled yesterday (commit id
>> e430510e5cbbfcdc1077739292def633e70fedea), compiled and installed on a
>> Debian unstable system. Dom0 kernel is a bit old, as it's a 3.6.
>>
>> What about you?
> xen 4.2.2
> kernel dom0: 3.8.11-200.fc18.x86_64

Just had an idea: is there any other load on the system during your test (other
domains, dom0 load)? If not, it could be that the power management is reducing
the cpu speed during idle (when the cap applies). This could lead to reduced
performance overall.

You can test this by setting the xen hypervisor boot option

cpufreq=none

and run your test again (with and without cap).


Juergen

-- 
Juergen Gross                 Principal Developer Operating Systems
PBG PDG ES&S SWE OS6                   Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@ts.fujitsu.com
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html