thanks Richard,

The experiment was indeed done with nested VM enabled. I am not sure about the internals, but i thought once overlay is setup the 2 main processes are sshd and qemu-img convert (reading data from sshd and doing the conversion)
I don't see any of the qemu process running.
Initial overlay setup was pretty quick and rest of the time was spent in qemu-img convert operation


On Wed, Apr 10, 2019 at 6:22 AM Richard W.M. Jones <> wrote:
On Tue, Apr 09, 2019 at 06:37:46PM -0700, Sureshkumar Kaliannan wrote:
> Hi,
> I'm trying to create a clone of a physical Window VM using p2v.
> My goal is to create a cloning tools VM that has libguestfs tools installed
> and acts as the convertor.
> VM conversion works just fine but the conversion rate is significantly
> slow(1/3) when running inside the VM compared to when the v2v is run on the
> same bare-metal host.
> On the host:
> ./virt-p2v-20190405-w1f4efxy/virt-v2v-conversion-log.txt:virtual copying
> rate: 615.9 M bits/sec
> ./virt-p2v-20190405-w1f4efxy/virt-v2v-conversion-log.txt:real copying rate:
> 181.8 M bits/sec
> >From the Guest VM (On the same bare-metal host)
> virt-p2v-20190405-95azj89j/virt-v2v-conversion-log.txt:virtual copying
> rate: 185.1 M bits/sec
> virt-p2v-20190405-95azj89j/virt-v2v-conversion-log.txt:real copying rate:
> 62.7 M bits/sec
> I understand there are several factors come into play but i tried to make
> the VM comparable by making sure enough CPU / memory is given to the VM.
> Also the I played by adjusting the disk cache modes for the VM(cache=none,
> cache=unsafe).  When the conversion happens there is not much load and
> there are no other VMs on this machine.
> I ruled out the disk being the bootleneck because when i do "virt-v2v -i
> disk" conversion the VM is only slightly off.
> For the same disk image,
> virt-v2v when running in the host took '75 sec' whereas in the VM it took
> '100 sec'
> How to go about debugging this performance issue? Any pointers would be
> helpful

I think this is just KVM vs TCG?  You could try enabling nested KVM to
see if that makes things faster, but it very much depends on your host


Richard Jones, Virtualization Group, Red Hat
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