← Back to team overview

kernel-packages team mailing list archive

[Bug 727459] Re: TSC is not reliable under Xen on some Intel CPUs


Having the same issue on Trusty

3.13.0-29-generic #53-Ubuntu SMP Wed Jun 4 21:00:20 UTC 2014 x86_64
x86_64 x86_64 GNU/Linux

This is occurring for me on some EC2 instances. Not continuously, but
sporadically when launching new instances.

I've attached a sample of the dmesg log showing the time jump.

** Attachment added: "Sample dmesg log with time jump"

You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.

  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:
Status in “linux” source package in Trusty:

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
  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


To manage notifications about this bug go to: