libvirt users - Sep 2014 - QEMU disk migration not using entire connection throughput

Hello everybody,

I've been observing that, during the disk migration usign 
--copy-storage-inc, the data transfer hardly ever uses the entire 
available connection bandwidth (in my case 1 Gb/s), and the migration is 
at a non-constant speed. On the other hand, at the memory migration 
step, everything goes perfect.

I am almost sure that this is not a nard disk throughput limitation, 
because a 'scp' command between the two same machines performs perfectly
right.

Is libvirt (or maybe QEMU?) doing some extra work that may cause slowlyness?

Thanks!