[libvirt-users] Live migration finish threshold

Hello everyone, Can somebody point where I can find the code where libvirt makes the decision to complete a live migration? I mean, at some point syncronising the VM state, it has to decide that the delta left to be migrate is low enough to achieve downtime 0, so libvirt finishes the migration. This "low enough" must be defined somewhere in the code, but I am unable to find it. Thank you very much.