** Description changed:
- From trusty through to vivid there is a copy_to/from_user patch that
- improved performance on the m400. This patch was not pushed into wily's
- 4.2 kernel as a new one was nearing upstream acceptance. That patch has
- now landed in linux-next and needs to be backported to wily's 4.2
- kernel.
+ [Impact]
+ 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.
+
+ [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. The backported patches have also been tested on
real arm64 hardware.
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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
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