Yes, it seems a lot like an iperf bug. I did the same test with uperf and got full bandwith. Even bonding works well:
ubuntu5# bmon # Interface RX Rate RX # TX Rate TX # ------------------------------------------------------------------- ubuntu5 (source: local) 0 br2 39.00B 0 377.00B 0 6 bond2 216.04MiB 213299 213.28MiB 179034 12 vnet0 106.83MiB 35932 107.96MiB 51115 15 eth1 103.92MiB 103566 102.63MiB 85928 17 eth2 112.11MiB 109715 110.58MiB 93057 22 vnet1 99.18MiB 32968 100.49MiB 49117 What I do not know is, why this occurs only with iperf on virtual machines talking to another iperf instance on the network. -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/1079212 Title: network slow when 2 VMs using virtio net bridged to same pyhs. network device on kvm host To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/iperf/+bug/1079212/+subscriptions -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
