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[Brad Figg <brad.figg@xxxxxxxxxxxxx>]

This bug is missing log files that will aid in diagnosing the problem.
>From a terminal window please run:

apport-collect 1516565

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable
to run this command, please add a comment stating that fact and change
the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the
Ubuntu Kernel Team.

** Changed in: linux (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1516565

Title:
  Strange kernel or scheduling problem

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  I see a strange kernel or scheduler problem with Kubuntu 15.04 and
  15.10.  I have Intel 3960X cpu with 6 cores (Hyperthreading is
  disabled). The problem is that when I run many CPU intensive
  applications (using full CPU), I cannot fully use all the cores of
  CPU. I tried a very simple app, which only multiplies some integers
  infinitly to emulate only high cpu usage with out any disk bottleneck.
  when I run multiple copies of the app, sometimes the scheduler assign
  all of them to a single core! Sometimes "top" shows that all CPU
  intensive apps are using only 0% CPU even though one of the cores is
  100% utilized and the apps are definitely working. Sometimes the apps
  cannot use the full CPU and the CPU usage of a single app oscillates
  between 0% to 100%. The problem becomes visible when there are 4 or
  more CPU intensive apps. When there are 6 apps, the mouse movement
  becomes sluggish and the system becomes very unresponsive even though
  the "top" shows that the CPUs are not fully used. I tried adding
  intel_pstate=disable in GRUB and setting scheduler to SCHED_ISO, but
  no effect.

  I tried different kernel versions previously installed. The current
  kernel 4.2.0 and the previous kernel 3.19.0 have this problem. Kernel
  version 3.11.0-19 worked without any problems.

  When I change a device driver( like the NVIDIA binary driver version),
  the problem is fixed until the next reboot. Probably changing a device
  driver is resetting the kernel and temporally fixing the problem.

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