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[dann frazier <dann.frazier@xxxxxxxxxxxxx>]

** Summary changed:

- transparent hugepages flaky on arm64
+ transparent hugepages flaky on arm64 and armhf

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https://bugs.launchpad.net/bugs/1309221

Title:
  transparent hugepages flaky on arm64 and armhf

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

Bug description:
  linux 3.13.0-24.46

  transparent hugepages, which are configured on by default in Ubuntu,
  are flaky on arm64. The most evident system is that go processes
  reliably hang or crash. This has been observed with both building
  juju-core with gccgo, and running the resulting juju binaries.

  The root cause of this is that get_user_pages_fast is not yet
  implemented on arm64 (and arm64). Patches are floating around, but
  haven't landed.

    http://comments.gmane.org/gmane.linux.ports.arm.kernel/299268

  We've verified that either applying those patches, or disabling THP
  via sysfs, prevents the above issues.

  At minimum we should change the default boottime sysfs setting for THP
  to "never" until we can fix this feature properly.

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