On Mon, 5 Jan 2009, Nathan Stratton wrote:
> 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.
Sorry to reply to my own post... We are running Centos 5.2
2.6.18-92.1.18.el5xen for Dom0 and DomUs with Xen 3.3.0.
><>
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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