[libvirt] blkio cgroup

[Dominik Klein]

> - Need little more info about how did you capture the blktrace. So you 
>   started blktrace and then started dd in parallel in all the three
>   VMs and immediately system freezes and these are the only logs we see
>   on console?

Almost ...

The ssh connection through which I start the vmstat and/or blktrace
never froze (not before, either). I can use that shell in the situation
until I try accessing anything on a block device.

So the blktrace was started before dd was started and blktrace was
stopped (CTRL+C) while dd was still running.

hth
Dominik