[Xen-users] Severe dom0 performance issues after installing Xen

[Keith Buck <buck.alex@xxxxxxxxx>]

Hello,

I'm experiencing some severe performance issues running Xen 4.0.1 with a 
cleanly-installed Debian 6 dom0.  Prior to installation, the machine's 
performance was fine, but after installation booting takes anywhere from 
5 to 20 times longer, processes take a long time to start, and SSH 
lags.  No domUs are running (or have been created yet).  I can switch 
back to running without Xen (but still using the Xen-compatible kernel) 
and the performance problems disappear.
I attempted to dig into the issue further, but haven't been able to find 
any reason why the machine is so slow.  Some cursory CPU integer 
performance and memory bandwidth benchmarks I ran showed that there is 
almost no difference in performance, and disk only loses about 10% of 
its performance.  I also haven't found anything particularly alarming in 
dmesg or xm dmesg (although this is my first time installing Xen, so I 
am not sure I would know what to look for).  top and xm top don't show 
anything constantly consuming all of the system's resources, and the 
only additional service I've installed so far is ntpd.  As an additional 
debugging step, I've attempted limiting the dom0 memory to 1536MB (the 
machine has 4GB of physical memory).  I haven't managed to turn up 
anything about this on Google yet.
Has anyone seen a similar issue before or have ideas on how to fix/debug 
it?  I have no physical access to the machine, unfortunately, so I am 
unable to play with BIOS settings.  I've attached the contents of dmesg 
and xm dmesg, should these be useful.
Thanks,
Keith

Attachment: dmesg
Description: Text document

Attachment: xm-dmesg
Description: Text document

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