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Old 10-26-2011, 02:44 PM
chicharras
 
Default kworker processes with very high CPU usage.

I am experiencing a nasty problem with my work laptop: Lenovo T61 -
Ubuntu 11.04 installed.

With a fresh reboot and only running System Monitor I see one of my
CPUs fluctuate from 5% utilization to 100% every 12 or so seconds.
The other CPU fluctuates with the same frequency from 5% to 40%.
Nothing other than System Monitor is running.
Once I start the applications I work with, I experience very annoying
periodic delays in response time.
The top command shows some "kworker" processes that are taking all the
CPU. Here is a snapshot:

top - 09:08:58 up 5 min, 2 users, load average: 0.86, 0.85, 0.41
Tasks: 151 total, 3 running, 147 sleeping, 0 stopped, 1 zombie
Cpu(s): 14.3%us, 34.7%sy, 0.0%ni, 51.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 3070088k total, 659492k used, 2410596k free, 62932k buffers
Swap: 3927888k total, 0k used, 3927888k free, 338940k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
10 root 20 0 0 0 0 S 66 0.0 1:21.81 kworker/0:1
1587 cesar 20 0 91680 19m 15m R 22 0.6 0:41.93 gnome-system-mo
878 root 20 0 61672 18m 8724 R 7 0.6 0:18.54 Xorg
1361 cesar 20 0 259m 46m 20m S 2 1.6 0:07.25 compiz
25 root 20 0 0 0 0 S 0 0.0 0:00.27 kworker/1:1

I always install all the updates offered by Update Manager. The last
entries in /var/log/dpkg.log show that yesterday I installed some PAM
stuff as shown by:

2011-10-25 07:47:32 upgrade libpam0g 1.1.2-2ubuntu8.3 1.1.2-2ubuntu8.4
etc...

and a new kernel:
2011-10-25 07:47:51 install linux-image-2.6.38-12-generic <none> 2.6.38-12.51
etc...

The problem exists even if I boot with my previous kernels. I have tested:
2.6.38-12-generic
2.6.38-11-generic
2.6.38-10-generic
2.6.38-8-generic

So, could this problem be caused by the updates to the PAM stuff?
Can anyone please indicate if and how I could roll back these updates?
Any pointers will be appreciated.

Note: I googled quite a while and found many hits but none are
conclusive to me. Like the following bug with kernel 2.6.37:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/717919


Thanks

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Old 10-26-2011, 06:02 PM
NoOp
 
Default kworker processes with very high CPU usage.

On 10/26/2011 07:44 AM, chicharras wrote:
> I am experiencing a nasty problem with my work laptop: Lenovo T61 -
> Ubuntu 11.04 installed.
>
> With a fresh reboot and only running System Monitor I see one of my
> CPUs fluctuate from 5% utilization to 100% every 12 or so seconds.
> The other CPU fluctuates with the same frequency from 5% to 40%.
> Nothing other than System Monitor is running.
> Once I start the applications I work with, I experience very annoying
> periodic delays in response time.
> The top command shows some "kworker" processes that are taking all the
> CPU. Here is a snapshot:
>
> top - 09:08:58 up 5 min, 2 users, load average: 0.86, 0.85, 0.41
> Tasks: 151 total, 3 running, 147 sleeping, 0 stopped, 1 zombie
> Cpu(s): 14.3%us, 34.7%sy, 0.0%ni, 51.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
> Mem: 3070088k total, 659492k used, 2410596k free, 62932k buffers
> Swap: 3927888k total, 0k used, 3927888k free, 338940k cached
>
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> 10 root 20 0 0 0 0 S 66 0.0 1:21.81 kworker/0:1
> 1587 cesar 20 0 91680 19m 15m R 22 0.6 0:41.93 gnome-system-mo
> 878 root 20 0 61672 18m 8724 R 7 0.6 0:18.54 Xorg
> 1361 cesar 20 0 259m 46m 20m S 2 1.6 0:07.25 compiz
> 25 root 20 0 0 0 0 S 0 0.0 0:00.27 kworker/1:1
>
> I always install all the updates offered by Update Manager. The last
> entries in /var/log/dpkg.log show that yesterday I installed some PAM
> stuff as shown by:
>
> 2011-10-25 07:47:32 upgrade libpam0g 1.1.2-2ubuntu8.3 1.1.2-2ubuntu8.4
> etc...
>
> and a new kernel:
> 2011-10-25 07:47:51 install linux-image-2.6.38-12-generic <none> 2.6.38-12.51
> etc...
>
> The problem exists even if I boot with my previous kernels. I have tested:
> 2.6.38-12-generic
> 2.6.38-11-generic
> 2.6.38-10-generic
> 2.6.38-8-generic
>
> So, could this problem be caused by the updates to the PAM stuff?
> Can anyone please indicate if and how I could roll back these updates?
> Any pointers will be appreciated.
>
> Note: I googled quite a while and found many hits but none are
> conclusive to me. Like the following bug with kernel 2.6.37:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/717919
>
>
> Thanks
>

This might be of interest w/some suggestions/related info:
http://ubuntuforums.org/showthread.php?t=1630347
[What is kworker?]

Seems as if even Linus Torvolds had issues:
https://lkml.org/lkml/2010/8/15/111
http://comments.gmane.org/gmane.linux.kernel/1023264



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Old 10-26-2011, 08:30 PM
chicharras
 
Default kworker processes with very high CPU usage.

On Wed, Oct 26, 2011 at 1:02 PM, NoOp <glgxg@sbcglobal.net> wrote:
> On 10/26/2011 07:44 AM, chicharras wrote:
>> I am experiencing a nasty problem with my work laptop: Lenovo T61 -
>> Ubuntu 11.04 installed.
>>
>> With a fresh reboot and only running System Monitor I see one of my
>> CPUs fluctuate from 5% utilization to 100% every 12 or so seconds.
>> The other CPU fluctuates with the same frequency from 5% to 40%.
>> Nothing other than System Monitor is running.
>> Once I start the applications I work with, I experience very annoying
>> periodic delays in response time.
>> The top command shows some "kworker" processes that are taking all the
>> CPU. Here is a snapshot:
<<< snip >>>
>> Note: I googled quite a while and found many hits but none are
>> conclusive to me. Like the following bug with kernel 2.6.37:
>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/717919
>>
>>
>> Thanks
>>
>
> This might be of interest w/some suggestions/related info:
> http://ubuntuforums.org/showthread.php?t=1630347
> [What is kworker?]
>
> Seems as if even Linus Torvolds had issues:
> https://lkml.org/lkml/2010/8/15/111
> http://comments.gmane.org/gmane.linux.kernel/1023264

Thank you very much for your help NoOp. I had seen that thread in
ubuntuforums, but I had missed the relevant post.
Your reference made me look closer and found the post that describes
my problem exactly.
My laptop has a bad ethernet port. I suppose the kworker process is
polling the port every few seconds.
I will disable it and buy a usb adapter.
Thanks again.

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Old 12-13-2011, 04:54 AM
terry
 
Default kworker processes with very high CPU usage.

After some extensive tests i would not use 11.04 or 11.10
with the kworker processes.
10.10 doesn't have this and is way faster.
I now will always test in VM first before any upgrading
as this took me 3 days and many installs to find out.

Best of luck



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Old 12-13-2011, 08:15 PM
NoOp
 
Default kworker processes with very high CPU usage.

On 12/12/2011 09:54 PM, terry wrote:
> After some extensive tests i would not use 11.04 or 11.10
> with the kworker processes.
> 10.10 doesn't have this and is way faster.
> I now will always test in VM first before any upgrading
> as this took me 3 days and many installs to find out.
...
You can join this bug report:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/887793
[Kworker constantly taking about 100% CPU ]

or this one:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/717919
[ACPI + kworker high interrupts. ]

And it's not just Ubuntu:
https://bugzilla.redhat.com/show_bug.cgi?id=638912
[Kworker/0 Task over 85%]




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