[Bug 1079212] Re: network slow when 2 VMs using virtio net bridged to same pyhs. network device on kvm host

[ITec]

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.

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https://bugs.launchpad.net/bugs/1079212

Title:
  network slow when 2 VMs using virtio net bridged to same pyhs. network
  device on kvm host

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