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I followed the steps on here Kworker, what is it and why is it hogging so much CPU? to try to figure out why there's a Kworker consuming a lot of CPU power.

Normally this wouldn't be an issue because I'm running a 4 core, 8 threaded machine, so one core couldn't hurt. But, when the core moves to CPU4, it makes my mouse stutter and the lighting on my keyboard (K70 RGB) to stop animating, so typing and moving the mouse becomes very difficult. If I reboot my machine, eventually it comes back and I can't seem to figure out what's causing it.

I've tried running echo l > /proc/sysrq-trigger but I get no ouput, and when I run perf record -g -a sleep 10 with perf report I get the following screen, but I'm not entirely sure about what I'm looking at.

screenshot

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Brian Leishman
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  • looks like that atheros card is misbehaving. what driver did you use? – j0h Nov 01 '15 at 16:39
  • I'm not entirely sure, how should I look that up? – Brian Leishman Nov 02 '15 at 13:55
  • Yes, it was my wireless card. If I disabled it, my CPU usage goes down completely and my computer runs nice ans smoothly. – Brian Leishman Nov 02 '15 at 23:31
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    @BrianLeishman I would still like to attempt to answer this question, both to claim the bounty, and help people with this issue in the future. can you run uname -r in a terminal and let me know the output please? – DeeJayh Nov 04 '15 at 17:06

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Do uname -r to check your kernel version, if it is before 2.6.30, I recommend upgrading it, which should fix any issues with that driver set.

  1. Go here: http://kernel.ubuntu.com/~kernel-ppa/mainline/ and pick a kernel to upgrade to. [http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.18.12-vivid/ is known working with most adapters in the 9k models]

  2. Download 3 (maybe 4) debs to a folder somewhere:

    linux-headers-VERSION-NUMBER_all.deb
linux-headers-VERSION-NUMBER_amd64.deb
linux-image-VERSION-NUMBER_amd64.deb
linux-image-extra-VERSION-NUMBER_amd64.deb   # if applicable

  3. Install the debs with whatever package manager front-end you use, or use these commands: cd /path/to/folder/where/you/put/the/debs sudo dpkg -i *.deb

If you're not interested in a kernel upgrade (you should be) or if it doesn't fix the issue as it presents, try installing backports meant to fix issues with the atheros 9k.

http://apt.ubuntu.com/p/linux-backports-modules-wireless-tahr-generic

The answer to this method can be found here, though I don't recommend hacking together what can be fixed with a simple kernel upgrade: How do I get the ath9k driver of backports-3.12-8 installed on Xubuntu 13.10?

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DeeJayh
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  • Unfortunately, I'm using kernel 3.19.0-28-generic, but since I posted the question we've found a work around that involved simply removing my wireless card and working around the need for one, so I can no longer test your suggestions. I've upvoted though, and if someone else upvotes as well then you will receive the bounty automatically – Brian Leishman Nov 04 '15 at 18:37
  • No problem, keep in mind though, to most people, disabling a piece of hardware is not a valid solution, only a temporary relief of the issue it's causing. Just because you cannot, or do not want to, test the solution, doesn't mean it shouldn't be the accepted answer. Glad you got it working though, to be honest, my ubu server is an old laptop, and I would likely have disabled it too, since I use a gigabit ethernet connection. Cheers! – DeeJayh Nov 04 '15 at 19:37
  • I understand that, I just don't know if I should accept an answer that I cannot test to ensure its validity, since I don't want someone in the future to use this as a perfect answer when it may not be, because I can't know for sure – Brian Leishman Nov 04 '15 at 19:53
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    Replace "cannot" with "will not", then "can't" with "won't", and you've got a solid comment :) It's fine, maybe I'll get lucky and someone will just happen to upvote my answer. – DeeJayh Nov 05 '15 at 04:46
  • If we get to the three days without I'll just grant you the bounty anyways. I still will not accept the answer, but there's no sense in just throwing away the extra rep – Brian Leishman Nov 05 '15 at 14:28