[Xen-users] Measure disk activity in full-virtualization.

["Alejandro Paredes" <aleparedes@xxxxxxxxx>]

I've been doing tests to compare the performance isolation between
para-virtualized and full-virtualized guests using Intel VT. First of
all we performed tests over 2 VM's (paravirtualized guest). Some bench
stressing memory and disk were done measured by xenmon and virt-top.
These two measure tools helped to determine CPU allocations, blocked
and waited times, and everything worked fine.

For measure disk usage, I understand that xenmon measures the transfer
of memory pages between DomU and Dom0, and virt-top could show VBD_RD
and VBD_WR for each VM. The problem arrived when measuring
full-virtualized guests. I can't measure de disk usage of a particular
VM. I know that the split device driver model used in
para-virtualization change by the complete emulation of the hardware.

I found that the process that handles the VM image is called qemu-dm.
When stressing disk activity of that VM (let's say VM1), no disk usage
of the qemu-dm process related to the VM1 is detected (using for
example pidstat over qemu-dm).Virt-top and xenmon didn't give me any
value reflecting disk usage when full-virtualized guest are stressed.

Is there any way to measure disk activity of a particular VM with full
virtualization?
Why virt-top and xenmon didn't give me any value?
Anybody tried something like this?

Thanks!

Alejandro.

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