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[Bug 1201869] Re: poor networking throughput across an OpenStack Neutron router on 3.5/3.8 kernels


** Branch linked: lp:ubuntu/quantal-proposed/linux-ti-omap4

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  poor networking throughput across an OpenStack Neutron router on
  3.5/3.8 kernels

Status in “linux” package in Ubuntu:
  Fix Released
Status in “linux” source package in Quantal:
  In Progress
Status in “linux” source package in Raring:
  In Progress

Bug description:
  SRU Justification:

  Users of the 3.5/3.8 kernel will have poor network throughput when using OpenStack Neutron depending on their setup.

  These patches are all in Ubuntu-3.9.0-7.15 / v3.9-rc1:

  Setup OpenStack Neutron. Test throughput between internal and external nodes.

  The following explains an example vlan+namespace configuration: 
  Internal Node: [10.x.x.2]->eth2.123->br123->tap123->qr-123[10.x.x.1] <--- netns: qrouter-123 
  netns: qrouter-123 ---> qg-234[10.x.y.1]->tap234->br234->eth2.234->External Node[10.x.y.2] 
  1) tap123+qr-123 and tap234+qg-234 are veth pairs
  2) qr-123 and qg-234 reside inside the qrouter-123 namespace


  OpenStack Neutron does IP forwarding through a network namespace. A
  veth pair is used to connect into the namespace. The veth pair appears
  to be the bottleneck, independent of network namespace. In newer
  versions of Linux (Ubuntu-3.9.0-7.15 / v3.9-rc1 and greater)
  throughput is much higher by almost 3 times. For example with some
  testing throughput is 3.5 Gbps in pre 3.9-rc1 versions and 9.1 Gbps
  with these patches applied.

  This has been confirmed on kernels from 3.5.x-3.8.x. (Quantal and
  Raring lts backports)

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