Very odd CPU in W2K8R2 guest after upgrading VirtIO


Hi all,

After upgrading to the most recent VirtIO drivers (from Fedora, version 0.1-65), I am noticing very weird CPU activity on my W2K8 R2 guests, that are running 2+ cores. Maybe someone can enlighten me … Please see attached screenshots for the details.

The host is Ubuntu 13.04, running kernel 3.8.0. System is built on two 6-core Intel E5-2630L processors, with 64MB of RAM (32MB for each). I upgraded the VirtIO storage, VirtIO NIC, and VirtIO Balloon drivers last Friday from, I believe, version 0.1-30 (July 2012). Another bit of info that might be of value – I also installed the “pm-utils” package for Ubuntu at the same time as upgrading the drivers, which was not installed previously.

In Windows, running the Performance Monitor, I notice that the processor counter “% C1 Time” is directly proportional to this weird activity. When the processor time shows ~20%+ and the total user/privileged CPU time is less than 1-2%, the % C1 Time is ~80% … And when the processor time is where I expect it should be (a total of the user+privileged time), the % C1 Time is at about 100%.

This particular screenshot shows the C1 time averaging about 90%, with the processor time averaging about 10%. Total CPU usage is around 1-2%, and idle CPU is 98-99%.

I don’t know whether or not the weird activity has something to do with pm-utils or the VirtIO drivers, nor do I know whether or not this is something I should be concerned about. Any thoughts, suggestions, or answers would be very much appreciated. Thank you so much.



Oops, I mean 64GB of RAM, and 32GB for each CPU. :oops:



I uninstalled pm-tools, and even dropped the number of cores to just one. Also rebooted the host server. Same odd CPU activity.

Though, come to think about it – while doing maintenance that day – I set both of their USB devices from USB to USB2 at this same time, when installing pm-tools and upgrading the VirtIO drivers.

Would that have anything to do with it? This coming weekend, after production hours, I’ll be downgrading the VirtIO drivers to see if they might be the culprit.

Until then … I would appreciate any advice or info that anyone has on this matter. The problem doesn’t seem to be affecting performance or reliability, so I am not very worried about it. Simply would like to know what I’m dealing with here. :shock:

Thanks again.