kernel-packages team mailing list archive

[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

@Joe, please open a new bug report for this. I am not sure that in your
case there will be the same unreasonable high process times in top. And
even if, the kernel version for EC2 in Precise had very special Xen
code. So it is unlikely the same bug re-surfacing. I believe "ubuntu-bug
linux" should work from the ec2 instance. If not you can report into a
file with "apport-cli --save <filename> linux" and the submit it from a
ubuntu desktop with "apport-cli <filename>".

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https://bugs.launchpad.net/bugs/727459

Title:
  TSC is not reliable under Xen on some Intel CPUs

Status in “linux” package in Ubuntu:
  Fix Released
Status in “linux” source package in Lucid:
  Triaged
Status in “linux” source package in Trusty:
  Triaged

Bug description:
  SRU Justification

  Impact: When applying the Xen patchset one endif seems to have gone to
  the wrong place. So instead of not setting sched_clock_stable it is
  done all the time.

  Fix: Move endif so the whole code segment is covered.

  Testcase: Can cause various effects and depends on CPU (see below).
  Incorrect CPU time but likely also causing the unexplainable process
  gets stuck or clone/fork issues.

  ---

  Ubuntu 10.04.2 LTS
  Ubuntu 2.6.32-312.24-ec2 2.6.32.27+drm33.12
  Linux 2.6.32-312-ec2 #24-Ubuntu SMP Fri Jan 7 18:30:50 UTC 2011 x86_64 GNU/Linux

  We are experiencing impossibly high (thousands of days) accumulated
  CPU times for processes in ps and top when using the above kernel on
  Amazon EC2.

  Instances running on Intel E5430 are fine, while instances on E5507 all seem to have the problem.
  Please see also https://bugzilla.kernel.org/show_bug.cgi?id=16314

  Thanks,
  Doug

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