[Bug 1586417] Re: Ubuntu 16.04 Desktop kworker/1:0 and systemd-timesync use 100% CPU, system very slow

[James]

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
>


** Attachment added: "dmesg.txt"
   https://bugs.launchpad.net/bugs/1586417/+attachment/4680726/+files/dmesg.txt

** Attachment added: "journal.txt"
   https://bugs.launchpad.net/bugs/1586417/+attachment/4680727/+files/journal.txt

** Attachment added: "dmesgintergraphics.txt"
   https://bugs.launchpad.net/bugs/1586417/+attachment/4680728/+files/dmesgintergraphics.txt

** Attachment added: "journalintelgraphics.txt"
   https://bugs.launchpad.net/bugs/1586417/+attachment/4680729/+files/journalintelgraphics.txt

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https://bugs.launchpad.net/bugs/1586417

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

Status in systemd package in Ubuntu:
  Incomplete

Bug description:
  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

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