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


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.


Attachment: dmesg
Description: Text document

Attachment: xm-dmesg
Description: Text document

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