[fedora-virt] Disk device performance in F11

[Jerry James]

I'm having a problem with a virtual machine created on an F-11 host
that I didn't have with an F-10 host, and I'm wondering if I've
misconfigured something or missed a trick somewhere.  I'm doing some
custom Linux kernel work for my employer, and I'm using a small
collection of virtual machines to test it.  In the short time I've had
F-11 on my host machine, I've seen that virtual disk performance is
noticeably worse than it was with F-10.  My virtual machines regularly
spew soft lockup messages to the system log, always with backtraces
that show the process is being starved of the disk.  The tests put a
lot of stress on the disk, because this custom kernel work is going to
help some overloaded servers deal with the load.

It's actually working pretty well on the real machines with real
disks, but with the upgrade to F-11, my test VMs have become almost
useless for testing further development work.  Before I take the
drastic step of rolling back to F-10, what factors affect the virtual
disk performance?

I created both the F-10 and F-11 machines with virt-manager, if that matters.

Thanks,
-- 
Jerry James
http://www.jamezone.org/