Most of us have probably seen this, where the kernel_taks starts using high amounts of CPU. There can be several causes for this but one I didnt even think about is CPU temperature. To offer so more clarity I have a 2012 MacBook Pro 10,1 – 2.7Ghz I7 16G memory. I had to replace my battery and used iFixit kit to do so and worked perfectly. When I opened it it was pretty dirty, even though I have blown out the fan ports from outside the case. In reality all this did was blow the dust around inside. When I had this open I thought about replacing my fans since its an older laptop and rarely gets shut off, but they seemed to spin fine with no noise.
So why am I blabbering about the battery being replaced, okay to the point. When I reassembled and brought it back up the fans were on full blast! They didn’t seem to want to slow down like it normally would have. So I used Mac Fan Control to slow down the fans according to CPU proximity temperature. Well low and behold the next day I had a kernel task running %400-%2200 ( yes this is not a typo).
kernel_task 418 27:18:43.46 279 219 0.0 0.00 0 root 0 bytes (null) - No No No 0 bytes 0 bytes 0 0 0 bytes 0 bytes 0 bytes 0 bytes 0 bytes 0 bytes No No (null) 0 bytes Yes
After doing some digging and running spindump I was able to find a blurb on someone having fan issues that was causing the high kernel %. I am speculating but since these have CPU turbo boost I wonder if it has something to do with that aside from the obvious that things run better cooler that’s just a fact. So realizing this could be an issue, I put my fans back to normal and they started adjusting automatically like it used to rather than maxed out. To provide full disclosure I did perform an SMC reset prior to missing with fan control.
kernel_task 5.5 12:22:14.88 279 429 0.0 0.00 0 root 0 bytes (null) - No No No 0 bytes 0 bytes 0 0 0 bytes 0 bytes 0 bytes 0 bytes 0 bytes 0 bytes No No (null) 0 bytes Yes
Now it’s much happier 11.9% and up, so what really happened? I am not sure why the fans went crazy and would not slow down and I let it go for a day. If I wouldn’t have run into this there would have been no reason for me to control the fan speed and I would never have seen this problem. So although this was self induced, if you ever have an issue where fans wont slow and kernel_task is high CPU its a safe bet that your fans may be going and time to replace.
Thanks for coming and stay frosty!