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[Adam Conrad <adconrad@xxxxxxx>]

** Changed in: linux (Ubuntu Quantal)
       Status: Fix Released => In Progress

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https://bugs.launchpad.net/bugs/1201869

Title:
  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:
  Fix Committed

Bug description:
  SRU Justification:

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

  Fix:
  These patches are all in Ubuntu-3.9.0-7.15 / v3.9-rc1:
  2681128f0ced8aa4e66f221197e183cc16d244fe
  8093315a91340bca52549044975d8c7f673b28a1
  d0e2c55e7c940a3ee91e9e23a2683b593690f1e9

  Testcase:
  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] 
  Where:
  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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