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Re: [Xen-devel] Performance difference between Xen versions

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Subject: Re: [Xen-devel] Performance difference between Xen versions
From: John Weekes <lists.xen@xxxxxxxxxxxxxxxxxx>
Date: Mon, 02 May 2011 20:39:50 -0700
Cc: "mark.langsdorf@xxxxxxx" <mark.langsdorf@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Wang, Winston L" <winston.l.wang@xxxxxxxxx>, "Wei, Gang" <gang.wei@xxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
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On 5/2/2011 8:04 PM, Tian, Kevin wrote:

you won't know the exact frequency bumped up in the turbo mode, as it's all 
by the CPU itself. what xen can do is just to tell the cpu now I'm OK to enter 
mode, which is 2268000 (1M higher than normal P0). Then CPU will decide whether
current code can be overclocked based on various conditions, such as TDP, other
core activities in the same package, ...

One possibility to verify that turbo mode does work is to run a CPU intensive 
on one core, while keeping other cores mostly idle. Then choose cpufreq governor
to be performance, and then compare your benchmark when BIOS turbo mode is
on/off. This should give you some feeling whether turbo mode works on your 

Thanks for the response, Kevin.

It's good to know that I can check turbo by looking to see if it's in the 1000hz-higher mode. It's a little strange to me that the true MHz level of the turbo wouldn't be known/shown, but I can live with that, as the actual performance is what counts. I'll run those benches.


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