Ubuntu 16.04 Desktop kworker/1:0 and systemd-timesync use 100% CPU, system very slow

[James]

Fairly new Ubuntu 16.04 Desktop installation with SSD hard drive, 64Gb memory. System runs OK for a day or two then desktop environment becomes completely unresponsive (display frozen).
You can ssh into it (very slow response when you enter the password) and "top" shows that the CPU is being 100% used by three processes:

top - 22:02:58 up 2:26, 4 users, load average: 18.00, 17.96, 15.87
Tasks: 293 total, 16 running, 274 sleeping, 0 stopped, 3 zombie
%Cpu(s): 0.9 us, 9.6 sy, 0.0 ni, 89.1 id, 0.4 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 64276428 total, 60695284 free, 2272164 used, 1308980 buff/cache
KiB Swap: 31412220 total, 31412220 free, 0 used. 61740156 avail Mem

  PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
 1278 systemd+ 20 0 96092 2360 2188 R 106.7 0.0 51:11.22 systemd-timesyn
   14 root 20 0 0 0 0 R 100.0 0.0 25:42.02 kworker/1:0
 6314 colord 20 0 280824 6060 5428 R 100.0 0.0 25:42.01 colord-sane
 2692 jrc 20 0 2869988 322548 271288 S 6.7 0.5 4:20.13 VirtualBox
    1 root 20 0 120208 6332 3936 D 0.0 0.0 0:01.77 systemd
    2 root 20 0 0 0 0 S 0.0 0.0 0:00.01 kthreadd
    3 root 20 0 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/0
    5 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:0H
    7 root 20 0 0 0 0 S 0.0 0.0 0:07.34 rcu_sched
    8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh
    9 root rt 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
   10 root rt 0 0 0 0 S 0.0 0.0 0:00.02 watchdog/0
   11 root rt 0 0 0 0 R 0.0 0.0 0:00.02 watchdog/1
   12 root rt 0 0 0 0 S 0.0 0.0 0:00.00 migration/1
   13 root 20 0 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/1
   15 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/1:0H
   16 root rt 0 0 0 0 R 0.0 0.0 0:00.02 watchdog/2
   17 root rt 0 0 0 0 R 0.0 0.0 0:00.00 migration/2
   18 root 20 0 0 0 0 S 0.0 0.0 0:00.04 ksoftirqd/2

Memory is clearly not an issue, but something seems to be making it hog CPU cycles and hang

[Peter Mahnke (peterm-ubuntu)]

Not sure where to file this, but not the ubuntu.com website.

[Martin Pitt (pitti)]

Pleeeeeeeease file bugs with "ubuntu-bug", not directly on Launchpad, to collect some actually useful information automatically.

Please run

   sudo journalctl -b > /tmp/journal.txt
   dmesg > /tmp/dmesg.txt

and attach both files here. Thanks!

[James (jrc-k)]

Sorry about the "ubuntu-bug" filing. I simply googled "report Ubuntu
bug" and Google sent me straight to the Launchpad method, so I assumed
that was the correct way to do it. If there is a better/preferred way it
certainly doesn't seem clear when searching online.

Attached are dmesg and journal as requested, run with the nvidia card,
which leads to the frequent GUI lockups and systemd-timesync 100% CPU loads

I have also conducted one more experiment where I removed the graphics
card and used the motherboard's onboard Intel graphics instead. That has
run stable with no lockups for two days, so it seems not to be affected
by the same problem. It may somehow be linked to the nvidia graphics,
whether run under nouveu or the proprietary driver. I also tried an
older Nvidia card (GV-N240D3-1GI, slightly fancy in its day, big cooling
fan) and had the same issues as with the newer one.

I am also attaching for your reference dmesg and journal when it's
running on the onboard intel graphics, in case comparing the two is
helpful. The onboard graphics seem pretty stable; the only odd artifact
I sometimes get is the screen going black for about half a second to one
second (for no reason I can readily ascertain) and then going back to
totally normal as though nothing had happened. In terms of impact this
minor niggle is easy to live with - certainly a lot easier than total
GUI lockup every few hours. The "brief black screen" episodes happen
every few hours as far as I can tell.

Unlike doing 'dmesg > filename.txt' , if I look in the logs directory,
'cat /var/log/dmesg' shows a very empty file - just one line saying
"(Nothing has been logged yet.)"

On Wednesday, June 08, 2016 10:30 PM, Martin Pitt wrote:
> Pleeeeeeeease file bugs with "ubuntu-bug", not directly on Launchpad, to
> collect some actually useful information automatically.
>
> Please run
>
> sudo journalctl -b > /tmp/journal.txt
> dmesg > /tmp/dmesg.txt
>
> and attach both files here. Thanks!
>
> ** Changed in: systemd (Ubuntu)
> Status: New => Incomplete
>

[Launchpad Janitor (janitor)]

[Expired for systemd (Ubuntu) because there has been no activity for 60 days.]