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[Launchpad Bug Tracker <1358949@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package linux - 3.16.0-10.15

---------------
linux (3.16.0-10.15) utopic; urgency=low

  [ dann frazier ]

  * [debian] Fix regression with ABI subversions and backport

  [ Feng Kan ]

  * SAUCE: (no-up) irqchip:gic: change access of gicc_ctrl register to read
    modify write.
    - LP: #1357527
  * SAUCE: (no-up) arm64: optimized copy_to_user and copy_from_user
    assembly code
    - LP: #1358949

  [ Stefan Bader ]

  * SAUCE: bcache: prevent crash on changing writeback_running
    - LP: #1357295

  [ Tim Gardner ]

  * [Config] CONFIG_XFRM_STATISTICS=y
  * [Config] CONFIG_SECURITY_NETWORK_XFRM=y
  * [Config] CONFIG_SENSORS_IBMPOWERNV=m
    - LP: #1353005
  * Release Tracking Bug
    - LP: #1359783

  [ Upstream Kernel Changes ]

  * intel_idle: Broadwell support
    - LP: #1256170
  * powerpc/book3s: Add basic infrastructure to handle HMI in Linux.
    - LP: #1357108
  * powerpc/powernv: Invoke opal call to handle hmi.
    - LP: #1357108
  * powerpc/book3s: handle HMIs for cpus in nap mode.
    - LP: #1357108
  * powerpc/book3s: Fix endianess issue for HMI handling on napping cpus.
    - LP: #1357108
  * powerpc: Add smp_mb() to arch_spin_is_locked()
    - LP: #1358569
  * powerpc: Add smp_mb()s to arch_spin_unlock_wait()
    - LP: #1358569
  * hwmon: (powerpc/powernv) hwmon driver for power, fan rpm, voltage and
    temperature
    - LP: #1353005
  * tools/testing/selftests/ptrace/peeksiginfo.c: add PAGE_SIZE definition
    - LP: #1358855
  * printk: Add function to return log buffer address and size
    - LP: #1359423
  * powerpc/powernv: Interface to register/unregister opal dump region
    - LP: #1359423
  * bcache: fix crash on shutdown in passthrough mode
    - LP: #1357295
  * bcache: fix uninterruptible sleep in writeback thread
    - LP: #1357295

  [ Vinayak Kale ]

  * SAUCE: (no-up) dt-bindings: Add Potenza PMU binding
    - LP: #1357527
  * SAUCE: (no-up) arm64: dts: Add PMU node for APM X-Gene Storm SOC
    - LP: #1357527
 -- Tim Gardner <tim.gardner@xxxxxxxxxxxxx>   Fri, 15 Aug 2014 12:34:33 -0600

** Changed in: linux (Ubuntu Utopic)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1358949

Title:
  arm64 iperf performance suboptimal

Status in “linux” package in Ubuntu:
  Fix Released
Status in “linux” source package in Trusty:
  Fix Committed
Status in “linux” source package in Utopic:
  Fix Released

Bug description:
  [Impact]
  The copy_{to,from}_user implementations in the Ubuntu kernel are suboptimal. Optimized implementations have been submitted upstream and have shown a significant improvement in network performance.

      Iperf performance increase:
                  -l (size)               1 core result
      Optimized   64B                     44-51Mb/s
                  1500B                   4.9Gb/s
                  30000B                  16.2Gb/s
      Original    64B                     34-50.7Mb/s
                  1500B                   4.7Gb/s
                  30000B                  14.5Gb/s

  [Test Case]
  Generate traffic from one node to another using iperf (see above for config).

  [Regression Risk]
  These functions are obviously used heavily throughout the kernel, so a defect here could have significant impact. This risk is mitigated by using an implementation heavily based on the linaro string libraries (which are used in other places already, e.g. glibc), and through active testing of this patch on real hardware using a trusty-kernel base.

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