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Message #147603
[Bug 1508471] Re: [SRU] arm64 performance regression in wily 4.2 kernel on m400 due to dropped patch
** Tags removed: verification-needed-wily
** Tags added: verification-done-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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References