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RE: [Xen-devel] [patch 14/33] xen: xen time implementation

To: "Mats Petersson" <Mats.Petersson@xxxxxxx>, "Keir Fraser" <keir@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [patch 14/33] xen: xen time implementation
From: "Jan Beulich" <jbeulich@xxxxxxxxxx>
Date: Wed, 06 Jun 2007 14:21:32 +0200
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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>> Yes, this could be an issue. Is there any way to get an 
>> interrupt or MCE
>> when thermal throttling occurs?
>
>As far as I'm aware, no. The normal way to "throttle" a procoessor is a
>Pulse-Width-modulation on the STOPCLK pin, and the duration is in the
>order of microseconds, so an interrupt every few microseconds may not
>leave much room for the processor to actually do ANYTHING at that point.
>
>
>Of course, it would be possible to design such hardware that does
>clock-throttling to indicate "Clock throttling started" and "clock
>throttling stopped" or some such, but as far as I'm aware, this is not
>how it works. 

There already is such an interrupt being generated (and used) on newer Intel
CPUs - see xen/arch/x86/cpu/mcheck/p4.c.

Jan


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