Tuesday, August 28, 2012

Mac OS X Lion: kernel_task with High CPU

My Mac has occasionally been going nuts and the fans start spinning up like crazy.  Tonight I sat down and took another stab at finding the culprit.

First I took at look with Activity Monitor but nothing obvious in My Processes.  So I switched to All Processes to see what root processes were doing.  Bingo, a nondescript Process Name called kernel_task was eating up just over 100% (110% before turning off some apps).

I read this article (Kernel_task process taking up an inordinate amount of CPU) at MacFixIt, which indicated to start cleaning stuff up (ya, I knew that, housekeeping). 

First I uninstalled some stuff that sounded good but which I just never use:
  • ShoveBox
  • Eye-Fi
Ok, CPU usage on kernel_task now down to about 104%.

Then I brought up the System Preferences -> Sharing panel.  In here I had Bluetooth sharing on for a previous project but I am not currently using it.  So I turned that off.

Bingo!  Kernel_task is down to about a peak of 4% CPU usage now in a steady state (ie. when I am not opening new processes).

The basic gist is that kernel_task is a catchall for a multitude of system processes and hence it can take some rooting around playing with settings to get it to decrease.  Good luck.


Jigga said...

kernel_task showing approx. 600% in activity monitor; been searching for a solution for about a fortnight and this finally worked! Thanks for the post.

Mariusz Pluciński said...

Helped me too. Without your post, I'd never think that enabled Bluetooth may be related to this issue. :)

JimJak said...

wow. fckng bluetooth ... it took me *weeks* to figure out why that kernel_task thing went out of control from time to time. I was about to send for the witchdoctor.

and now I come here, read about the related bluetooth issue, tick it off and on, and the kernel_task goes back to normal ... funny thing.

great, Mr. Drool you really made my day a happy one.
your share of experience is much appreciated.

Unknown said...

Using duster on the air vents of my MacBook Pro just dropped kernel_task from 22000% to 2.3%.