[Xen-users] Clock wobble

[Nathan Stratton <nathan@xxxxxxxxxxxx>]

We are building video/audio applications running on xen and have run into 
some major timing issues due to xen DomU clock wobble. My routers in each 
city act as NTP servers to the Dom0s. If I watch the clocks with ntpdate 
-q {cisco NTP server} I see wobble of 2 - 4 ms on the Dom0s. However with 
xen.independent_wallclock=0 I see wobble from -5 to -150 ms. I have tried 
to set xen.independent_wallclock=1 and use NTP, but that does not help 
because the clock still drifts between NTP updates.
My issue is drifting back and forth over the window between when the Dom0 
updates the DomU or between NTP updates if xen.independent_wallclock is 
set to 1. It does not look like it matters if it is a full or para DomU.
I have been looking at running a real time kernel, but so far have not 
been able to get that to run on xen.
Any ideas? Overall my clocks don't drift more then 200 ms, but when your 
mixing audio and video that is a big deal.
P.S. I also have played around with permitted_clock_jitter, but it does 
not seam to do anything.
> <>
Nathan Stratton                                CTO, BlinkMind, Inc.
nathan at robotics.net                         nathan at blinkmind.com
http://www.robotics.net                        http://www.blinkmind.com

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