CentOS - Jan 2008 - Xen clock drift

Hello All,

Consider a CentOS-5.1 Xen server (2.6.18-53.1.4.el5xen) hosting two 
domains running CentOS-5.1 (2.6.18-53.1.4.el5).  One domain has a fairly 
accurate clock, the other domain has a clock that gains ungodly amounts 
of time, roughly one minute every two or three minutes.  For a fix, one 
suggestion is to run this command in DomU:

echo 1 > /proc/sys/xen/independent_wallclock

This didn't change anything.  As an experiment, I wrote a script to call 
ntpd -q, sleep 60, and repeat indefinitely.  Here are a couple of 
snippets of output:

goodclock# ksh ./xenclockdrift  
ntpd: time slew +0.001211s
ntpd: time slew +0.001200s
ntpd: time slew +0.001855s
ntpd: time slew +0.001532s
ntpd: time slew +0.001603s
ntpd: time slew +0.001320s
ntpd: time slew +0.001931s

badclock# ksh ./xenclockdrift  
ntpd: time slew -0.000193s
ntpd: time set -57.356377s
ntpd: time slew +0.002352s
ntpd: time slew +0.003018s
ntpd: time set -57.417488s
ntpd: time slew +0.012089s
ntpd: time slew -0.000985s

These domains are fully virtualized and set up identically, except 
"badclock" is allocated two processors versus one processor for 
"goodclock".  DomU's clock is running normally.

Anyone know what's going or know how to fix it?

Jack

Jack Bailey wrote:
> These domains are fully virtualized and set up identically, except
> "badclock" is allocated two processors versus one processor for
> "goodclock".  DomU's clock is running normally.
> 
> Anyone know what's going or know how to fix it?
This is a known issue that has come up on this list a lot.

For C5.1 see the first known issue:

http://wiki.centos.org/Manuals/ReleaseNotes/CentOS5.1/

Rick