Kernel_task occuping one core, and writing excessively to SSD

[T'hain Esh Kelch]

Any solutions to such a problem? I can't force quit kernel_task, and it constantly hovers above 100% CPU. But far worse is that it writes 150 MB/sec constantly. My computer has idled a couple of days, and I just came back to the machine making regular hickups (Everything freezes for a few seconds) - Looked up Activity Viewer, and behold, kernel_task had written just over 800TB (!!) data!

Spotlight also appeared to be active in Activity Viewer, so I tried force quitting that, and resetting the index database, to no avail. Rebooted. Shut down, then started, no changes. Gotten so desperate I upgraded from MacOS Sequia 15.7.2 to Tahoe 26.1, and that also didn't make a difference. I set the machine to install, and when I came back an hour later, kernel_task had already written 100GB data to the disk, without me even being logged in!

This is on an M4 Pro mini, with 24GB RAM, and 1TB SSD. Only 50% of the RAM is being used on a fresh boot, swap disk is a 0 bytes after an hour, but kernel_task just keeps going... The weird thing is that it writes ~150MB/sec for ~30 seconds, then pauses completely for ~10 seconds, then repeats.

 

[T'hain Esh Kelch]

Huh, what do you know, after having done this for hours, it just randomly stopped. I wonder if it is because the kernel was updated during the Tahoe upgrade. What I did notice though, was that I at the exact same time got several delayed Reminders popups, and a notification that my Focus was automatically shut off.

I will keep an eye on this for the future, and use this thread to log observations. The rampaging kernel_task has done this before, and I don't know how I fixed it last time, although I have a vague recollection of it being related to Spotlight.

 

[chabig]

Kernel_task is a system process in macOS that manages the CPU's temperature and limits its resources to prevent overheating. It helps regulate the performance of your Mac by reducing CPU availability when it detects high temperatures. I assume your system was getting warm following the Tahoe upgrade, probably doing housekeeping tasks. As it completed those, temperature came down and kernel_task settled down.

If kernel_task is using a large percentage of your Mac CPU - Apple Support

One of the functions of the kernel task process is to help manage the temperature of your CPU.

support.apple.com