[Bug 1602755] Re: Tunnel offload indications not stripped from encapsulated packets, causing performance overhead

[Stefan Bader]

This bug is awaiting verification that the kernel in -proposed solves
the problem. Please test the kernel and update this bug with the
results. If the problem is solved, change the tag 'verification-needed-
xenial' to 'verification-done-xenial'.

If verification is not done by 5 working days from today, this fix will
be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
to enable and use -proposed. Thank you!


** Tags added: verification-needed-xenial

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https://bugs.launchpad.net/bugs/1602755

Title:
  Tunnel offload indications not stripped from encapsulated packets,
  causing performance overhead

Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Xenial:
  Fix Committed

Bug description:
  Commit:
  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit?id=a09a4c8dd1ec7f830e1fb9e59eb72bddc965d168

  Description:

  tunnels: Remove encapsulation offloads on decap.

  If a packet is either locally encapsulated or processed through GRO
  it is marked with the offloads that it requires. However, when it is
  decapsulated these tunnel offload indications are not removed. This
  means that if we receive an encapsulated TCP packet, aggregate it with
  GRO, decapsulate, and retransmit the resulting frame on a NIC that does
  not support encapsulation, we won't be able to take advantage of hardware
  offloads even though it is just a simple TCP packet at this point.

  This fixes the problem by stripping off encapsulation offload indications
  when packets are decapsulated.

  The performance impacts of this bug are significant. In a test where a
  Geneve encapsulated TCP stream is sent to a hypervisor, GRO'ed, decapsulated,
  and bridged to a VM performance is improved by 60% (5Gbps->8Gbps) as a
  result of avoiding unnecessary segmentation at the VM tap interface.

  Reported-by: Ramu Ramamurthy <sramamur at linux.vnet.ibm.com>
  Fixes: 68c33163 ("v4 GRE: Add TCP segmentation offload for GRE")
  Signed-off-by: Jesse Gross <jesse at kernel.org>
  Signed-off-by: David S. Miller <davem at davemloft.net>

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