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[Launchpad Bug Tracker <1384579@xxxxxxxxxxxxxxxxxx>]

[Expired for neutron because there has been no activity for 60 days.]

** Changed in: neutron
       Status: Incomplete => Expired

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https://bugs.launchpad.net/bugs/1384579

Title:
  Slow network outbound throughput with tso enabled in veth pair with
  newer kernels

Status in neutron:
  Expired
Status in OpenStack Compute (nova):
  Invalid

Bug description:
  Hi all,

  first of, this isn't really a bug report but a request for a
  workaround.

  With (obviously) kernels below 3.8 and OpenVSwitch < 2.0.0 the tcp
  segmentaion offload was off by default:

  $ ethtool -k qvb056d020b-d6
  Offload parameters for qvb056d020b-d6:
  rx-checksumming: off
  tx-checksumming: off
  scatter-gather: off
  tcp-segmentation-offload: off
  udp-fragmentation-offload: off
  generic-segmentation-offload: off
  generic-receive-offload: on
  large-receive-offload: off
  rx-vlan-offload: off
  tx-vlan-offload: off
  ntuple-filters: off
  receive-hashing: off

  With newer kernels (3.16.3-200.fc20.x86_64 in our case) tso is on by default which leads to slow outbound speed:
  Features for qvb5979dad2-b3:
  rx-checksumming: on
  tx-checksumming: on
  	tx-checksum-ipv4: off [fixed]
  	tx-checksum-ip-generic: on
  	tx-checksum-ipv6: off [fixed]
  	tx-checksum-fcoe-crc: off [fixed]
  	tx-checksum-sctp: off [fixed]
  scatter-gather: on
  	tx-scatter-gather: on
  	tx-scatter-gather-fraglist: on
  tcp-segmentation-offload: on
  	tx-tcp-segmentation: on
  	tx-tcp-ecn-segmentation: on
  	tx-tcp6-segmentation: on
  udp-fragmentation-offload: on
  generic-segmentation-offload: on
  generic-receive-offload: on
  large-receive-offload: off [fixed]
  rx-vlan-offload: on
  tx-vlan-offload: on
  ntuple-filters: off [fixed]
  receive-hashing: off [fixed]
  highdma: on
  rx-vlan-filter: off [fixed]
  vlan-challenged: off [fixed]
  tx-lockless: on [fixed]
  netns-local: off [fixed]
  tx-gso-robust: off [fixed]
  tx-fcoe-segmentation: off [fixed]
  tx-gre-segmentation: on
  tx-ipip-segmentation: on
  tx-sit-segmentation: on
  tx-udp_tnl-segmentation: on
  tx-mpls-segmentation: off [fixed]
  fcoe-mtu: off [fixed]
  tx-nocache-copy: off
  loopback: off [fixed]
  rx-fcs: off [fixed]
  rx-all: off [fixed]
  tx-vlan-stag-hw-insert: on
  rx-vlan-stag-hw-parse: on
  rx-vlan-stag-filter: off [fixed]
  l2-fwd-offload: off [fixed]
  busy-poll: off [fixed]

  Another workaround would be to disable tso in every VM which is using
  the virtio net driver which is often impossible since VMs are managed
  by customers.

  After creation of the veth pair a ethtool -K qvbXXX tso off should be
  triggered.

  Relevant used versions:
  kernel-3.16.6-200.fc20.x86_64
  openvswitch-2.3.0-1.fc20.x86_64
  qemu-system-x86-1.6.2-8.fc20.x86_64

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