[ovs-dev] [PATCH v3 0/3] Add support for TSO with DPDK

[Flavio Leitner]

Abbreviated as TSO, TCP Segmentation Offload is a feature which enables
the network stack to delegate the TCP segmentation to the NIC reducing
the per packet CPU overhead.

A guest using vhost-user interface with TSO enabled can send TCP packets
much bigger than the MTU, which saves CPU cycles normally used to break
the packets down to MTU size and to calculate checksums.

It also saves CPU cycles used to parse multiple packets/headers during
the packet processing inside virtual switch.

If the destination of the packet is another guest in the same host, then
the same big packet can be sent through a vhost-user interface skipping
the segmentation completely. However, if the destination is not local,
the NIC hardware is instructed to do the TCP segmentation and checksum
calculation.

The first 2 patches are not really part of TSO support, but they are
required to make sure everything works.

There are good improvements sending to or receiving from veth pairs or
tap devices as well. See the iperf3 results below:

[*] veth with ethtool tx off.

VM sending to:          Default           Enabled
   Local BR           859 Mbits/sec     9.23 Gbits/sec
   Net NS (veth)      965 Mbits/sec[*]  9.74 Gbits/sec
   VM (same host)    2.54 Gbits/sec     22.4 Gbits/sec
   Ext Host          10.3 Gbits/sec     35.0 Gbits/sec
   Ext Host (vxlan)  8.77 Gbits/sec     (not supported)

  Using VLAN:
   Local BR           877 Mbits/sec     9.49 Gbits/sec
   VM (same host)    2.35 Gbits/sec     23.3 Gbits/sec
   Ext Host          5.84 Gbits/sec     34.6 Gbits/sec

  Using IPv6:
   Net NS (veth)      937 Mbits/sec[*]  9.32 Gbits/sec
   VM (same host)    2.53 Gbits/sec     21.1 Gbits/sec
   Ext Host          8.66 Gbits/sec     37.7 Gbits/sec

  Conntrack:
   No packet changes: 1.41 Gbits/sec    33.1 Gbits/sec

VM receiving from:
   Local BR           221 Mbits/sec     220 Mbits/sec
   Net NS (veth)      221 Mbits/sec[*]  5.91 Gbits/sec
   VM (same host)    4.79 Gbits/sec     22.2 Gbits/sec
   Ext Host          10.6 Gbits/sec     10.7 Gbits/sec
   Ext Host (vxlan)  5.82 Gbits/sec     (not supported)

  Using VLAN:
   Local BR           223 Mbits/sec     219 Mbits/sec
   VM (same host)    4.21 Gbits/sec     24.1 Gbits/sec
   Ext Host          10.3 Gbits/sec     10.2 Gbits/sec

  Using IPv6:
   Net NS (veth)      217 Mbits/sec[*]  9.32 Gbits/sec
   VM (same host)    4.26 Gbits/sec     23.3 Gbits/sec
   Ext Host          9.99 Gbits/sec     10.1 Gbits/sec

Used iperf3 -u to test UDP traffic limited at default 1Mbits/sec
and noticed no change with the exception for tunneled packets (not
supported).

Travis, AppVeyor, and Cirrus-ci passed.

Flavio Leitner (3):
  dp-packet: preserve headroom when cloning a pkt batch
  vhost: Disable multi-segmented buffers
  netdev-dpdk: Add TCP Segmentation Offload support

 Documentation/automake.mk           |   1 +
 Documentation/topics/dpdk/index.rst |   1 +
 Documentation/topics/dpdk/tso.rst   |  96 +++++++++
 NEWS                                |   1 +
 lib/automake.mk                     |   2 +
 lib/conntrack.c                     |  29 ++-
 lib/dp-packet.h                     | 158 +++++++++++++-
 lib/ipf.c                           |  32 +--
 lib/netdev-dpdk.c                   | 318 ++++++++++++++++++++++++----
 lib/netdev-linux-private.h          |   4 +
 lib/netdev-linux.c                  | 296 +++++++++++++++++++++++---
 lib/netdev-provider.h               |  10 +
 lib/netdev.c                        |  66 +++++-
 lib/tso.c                           |  54 +++++
 lib/tso.h                           |  23 ++
 vswitchd/bridge.c                   |   2 +
 vswitchd/vswitch.xml                |  12 ++
 17 files changed, 1013 insertions(+), 92 deletions(-)
 create mode 100644 Documentation/topics/dpdk/tso.rst
 create mode 100644 lib/tso.c
 create mode 100644 lib/tso.h

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2.24.1