On Jun 26, 2014, at 2:50 AM, Eric Blake <eblake@redhat.com> wrote:

I'm still not clear how you are getting vcpu PID numbers for reading
from /proc; it's not something that libvirt is currently advertising.

I thought the VM process’s /proc statistics information is exactly the same 
as the guest’s behaviour. It turns out to be my misunderstanding.

Each vcpu is a thread of the VM process in qemu implementation, whose 
thread id can be obtained by the “-L” option of the “ps” command.  It seems 
that I don't mention the vcpu PID. I’m referring to the VM process’s /proc/$pid.

If running a VM whose image file is located on the local disk, how can i 
calculate the disk bandwidth(the percentage, e.g. 40% disk) used by the VM?