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[Xen-devel] How to increase timer resolution?

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] How to increase timer resolution?
From: Robert Kaiser <kaiser@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Sun, 14 Sep 2008 08:06:28 +0200
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Hi everyone,

I'm using Xen 3.2.1 in my experimental setup, trying to find relationships 
between switch frequencies and overheads. For that, it would be good if I 
could increase the resolution of the  timer (i.e. the one that you access 
with set_timer(), stop_timer() and friends). Currently, this seems to be 
fixed at 10 milliseconds, but I would like to change it to 1ms or maybe even 
down to a few hundred microseconds. I'm aware that this will affect 
performance --  that is part of what I'd like to measure.

Can you experts give me some hints how to do this, i.e. is it just a matter of 
giving the kernel the right commandline options (which?), can it be done by 
changing a few compile time constants   (which? where?), or is there more 

Ideally, I would implement a new control function by which dom0 could change 
the frequency dynamically at run-time, but even having to re-compile Xen 
between experiments might be an acceptable approach. However, the code base 
is so dauntingly huge for a newbie like myself, I'm having difficulties in 
finding the right set-screws.  Can anyone help me out?



Robert Kaiser                    http://wwwvs.informatik.fh-wiesbaden.de
Labor für Verteilte Systeme            kaiser@xxxxxxxxxxxxxxxxxxxxxxxxxx
FH Wiesbaden - University of Applied Sciences     tel: (+49)611-9495-1294
Kurt-Schumacher-Ring 18, 65197 Wiesbaden, Germany fax: (+49)611-9495-1289

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