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[Luis Henriques <luis.henriques@xxxxxxxxxxxxx>]

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-
wily' to 'verification-done-wily'.

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-wily

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https://bugs.launchpad.net/bugs/1508471

Title:
  [SRU] arm64 performance regression in wily 4.2 kernel on m400 due to
  dropped patch

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Wily:
  Fix Committed

Bug description:
  [Impact]
  Performance Regression.

  The copy_{to,from}_user implementations in the Ubuntu kernel are
  suboptimal. Optimized implementations have been accepted upstream and
  have shown a significant improvement in network performance. Previous
  Ubuntu releases included non-upstream versions of these patches, but
  they were dropped during the wily cycle.

  [Test Case]
  Generate traffic from one node to another using iperf.

  [Regression Risk]
  These functions are obviously used heavily throughout the kernel, so a defect here could have significant impact. However, it has been accepted by upstream after some cycles of review, and we have shipped earlier versions of it in every arm64 release prior to wily. The backported patches have also been tested on real arm64 hardware.

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