I have a 13" MBP late 2009, 2.53 GHz, 4 GB RAM, and on OS X 10.8.3. As soon as I boot up the fans start going at the highest rpm and like I mentioned the kernel_task is always at around 90% when no apps are being run. I read somewhere that I should try safe boot and see the effect but there is none. Any ideas as to what is causing it?


  • Open Terminal and type sudo iosnoop to show harddisk activity. Do you see lots of output to the command? If that's the case, could you add several lines of ouput to your question? Still in Terminal, type sudo tail -f /var/log/system.log to open and follow the system log. Are there warnings or errors? (Exit tail with <Ctrl>-C.) Again, it would be helpful that you shared your findings in your question.
    – jaume
    Commented May 30, 2013 at 7:42
  • I gave up on fixing a friend's Macbook Air for exactly this (well, CPU over 100%), tried most of the suggestions in that link and decided maybe the heat sensors (new logic board) were faulty. Sent her to Genius Bar. Commented May 30, 2013 at 8:11
  • I typed sudo iosnoop, and there was a bunch of output but i'm not too sure what is exactly relevant. But there was this line...dtrace: error on enabled probe ID 4 (ID 1031: io:mach_kernel:buf_strategy:start): illegal operation in action #3 at DIF offset 0. As for the system.log there wasn't much but there was this May 30 11:17:48 Pablos-MacBook-Pro.local coresymbolicationd[877]: /System/Library/Caches/com.apple.coresymbolicationd/data does not exist, resetting cache May 30 11:24:59 Pablos-MacBook-Pro.local login[882]: in pam_sm_acct_mgmt(): OpenDirectory - Membership cache TTL set to 1800. Commented May 30, 2013 at 16:27
  • Thanks for your help btw, and Andrew by the heat sensors being faulty you mean that it came out of the box being faulty or it happened over time? Oh and you said maybe, does that mean there's no way to actually tell? Commented May 30, 2013 at 16:31

2 Answers 2


It might actually be spotlight trying to index your drive.

  • that's shown once you open spotlight right? I mean it does say indexing files under the search bar yea? If so I don't think it's indexing files. but thanks anyways Commented May 30, 2013 at 5:23
  • To make this answer more useable in the future: How could the user find out whether it's really Spotlight indexing causing the high load?
    – nohillside
    Commented May 30, 2013 at 8:17
  • @patrix good point...found the answer "You will see a dot in the middle of the spotlight magnifying glass, and when you click on spotlight it will tell you that its indexing" forums.macrumors.com/showthread.php?t=376478 Commented May 30, 2013 at 16:44

I found a way to fix this issue, thought I should post it since it might help someone else. Granted this fix kinda worked for me since my fans are at their full rpm but you should read the explanation first and then choose to follow the steps yourself, anyways the info. is here: http://www.rdoxenham.com/?p=259

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