I'm using the virt-manager GUI 0.9.5-1ubuntu3 on my laptop running Ubuntu 14.04 against a server located some distance away (same OS) and getting rather unpleasant performance.
Laptop-server pings are ~50ms, not great but certainly sufficient for SSH access and even ok-ish running Firefox over X/ssh. Both server & laptop have plenty of spare CPU cycles, RAM and disks. My local ADSL is 8Mbps down 800Kbps upstream and exceptionally, the wife isn't streaming some soap ;-)
I'm creating a fresh VM and selecting 'customize config before install'. Clicking the 'Add Hardware' button freezes virt-manager for about 40 secs, during which little network activity occurs (117 kB sent, 151 kB rec'd, with peaks of 5kBps down, 11kBps up); CPU/RAM are absolutely fine on both boxes.
Pressing 'Finish' on the 'Add New Virtual Hardware' dialog to add a NIC takes 50s with similar bandwidth stats.
By contrast, the actual VM creation (35GB QCOW2 img) takes about 15 secs and console access performance via virt-manager is great - not significantly slower than SSH.
I must be doing smth wrong but what?