I have been experiencing this exact same issue since upgrading to Monterey 12.0.1. I believe I've discovered what triggers it - at least on the MacBook Pro hardware (mine is Intel CPU).
My suspicion is that the issue is related to power management in some way. I don't know enough about reading or understanding a spindump file to confirm.
Here is what I have tested and confirmed did NOT work for me:
- I thought the issue was related to Spotlight index so I disabled several index categories in Spotlight settings. Ultimately I also disabled Spotlight, completely deleted my index, re-enabled Spotlight, and rebuilt the entire index. This did not solve the issue.
- I tried booting in Safe Mode. This did not solve the issue.
- I reset NVRAM and SMC. Neither solved the issue.
- I booted in Recovery Mode and ran first aid on all volumes. This did not solve the issue.
- I modified/disabled several system preferences settings mentioned in other threads including: graphics switching, optimized battery charging, and reduce transparency. None of those solved the issue.
Ultimately I discovered the following:
- When the battery is low and I plug the computer into charge, kernel_task ends up consuming almost the entire CPU capacity within 60 seconds. It will quickly rise to 450% and stay anywhere between that number and upwards of 600%.
- It does this regardless of whether applications are open or not.
- If I unplug the power cable, the kernel_task process returns to the 3% - 6% range.
- If I re-plug the power cable, the kernel_task process jumps back up to the 450% - 600% range.
- Once the battery reaches a charge of 70%, the kernel_task process returns to the 3% - 6% range.
- It doesn't matter what power charger I use. Tested with 2 variations I have:
- Apple (OEM) 87W USB-C Power Adapter
- Anker Power Port III 65W USB-C Power Adapter
Sorry that this does not immediately suggest a good reason as to why you are experiencing the same issue since you're on an iMac which never transitions between AC and battery. But thought I would share what I have found incase it helps put others on the right path. Perhaps there is a shared power management issue I'm just not familiar with. This has been super frustrating given the fact that it essentially bricks all other usage of the computer because kernel_task is consuming all available resources. Interested to hear if anyone else suffering this issue can duplicate and confirm what I have seen.
Details of my hardware and software are:
macOS Monterey 12.0.1
MacBookPro14,3 (15-inch, 2017, touch bar)
2.9 GHz Quad-Core Intel i7
16GB RAM
Radeon Pro 560 4 GB / Intel HD 630 1536 MB
