Update and request from upstream:

"I have looked at the dump and there is something very odd for
system.slice task group where the display manager is running.
system.slice->tg_load_avg is around 381697 but  tg_load_avg is
normally equal to Sum of system.slice[cpu]->tg_load_avg_contrib
whereas Sum of system.slice[cpu]->tg_load_avg_contrib = 1013 in our
case. We can have some differences because the dump of
/proc/shed_debug is not atomic and some changes can happen but nothing
like this difference.

The main effect of this quite high value is that the weight/prio of
the sched_entity that represents system.slice in root cfs_rq is very
low (lower than task with the smallest nice prio) so the system.slice
task group will not get the CPU quite often compared to the user.slice
task group: less than 1% for the system.slice where lightDM and xorg
are running compared 99% for the user.slice where the stress tasks are
running. This is confirmed by the se->avg.util_avg value of the task
groups which reflect how much time each task group is effectively
running on a CPU:
system.slice[CPU3].se->avg.util_avg = 8 whereas
user.slice[CPU3].se->avg.util_avg = 991

This difference of weight/priority explains why the system becomes
unresponsive. For now, I can't explain is why
system.slice->tg_load_avg = 381697 whereas is should be around 1013
and how the patch can generate this situation.

Is it possible to have a dump of /proc/sched_debug before starting
stress command ? to check if the problem is there from the beginning
but not seen because not overloaded. Or if it the problem comes when
user starts to load the system"

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

  X1Carbon comes to a crawl during high CPU usage tasks

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Yakkety:
  In Progress

Bug description:
  My X1Carbon becomes quite laggy, the cursor hangs for a few seconds
  and then resumes while my system is compiling some code, or lets says
  PyCharm is indexing things or Android Studio is compiling some code. I
  was using 4.4 on Xenial a few days ago and everything was working just
  fine. Installed Yakkety and this issue happens.

  `stress -c 4` <-- that results in system slowness.

  I will downgrade the kernel and see if that mitigates the issue.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.10
  Package: linux-image-4.8.0-15-generic 4.8.0-15.16
  ProcVersionSignature: Ubuntu 4.8.0-15.16-generic 4.8.0-rc7
  Uname: Linux 4.8.0-15-generic x86_64
  ApportVersion: 2.20.3-0ubuntu7
  Architecture: amd64
   /dev/snd/pcmC1D0p:   om26er     3390 F...m pulseaudio
   /dev/snd/controlC1:  om26er     3390 F.... pulseaudio
   /dev/snd/controlC0:  om26er     3390 F.... pulseaudio
  CurrentDesktop: Unity
  Date: Fri Sep 23 21:40:34 2016
  HibernationDevice: RESUME=UUID=a92c85ab-cca3-4afc-abf1-3516f193129e
  InstallationDate: Installed on 2016-09-21 (1 days ago)
  InstallationMedia: Ubuntu 16.10 "Yakkety Yak" - Alpha amd64 (20160921)
  MachineType: LENOVO 20BSCTO1WW
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.8.0-15-generic.efi.signed 
root=UUID=01b0a4a0-d791-46e8-a212-1f769cff3a4b ro quiet splash vt.handoff=7
   linux-restricted-modules-4.8.0-15-generic N/A
   linux-backports-modules-4.8.0-15-generic  N/A
   linux-firmware                            1.161
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 08/13/2015
  dmi.bios.vendor: LENOVO
  dmi.bios.version: N14ET32W (1.10 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 20BSCTO1WW
  dmi.board.vendor: LENOVO
  dmi.board.version: SDK0E50510 WIN
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: None
  dmi.product.name: 20BSCTO1WW
  dmi.product.version: ThinkPad X1 Carbon 3rd
  dmi.sys.vendor: LENOVO

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