[Solved] WindowServer and kerneltask using a lot of CPU in Big Sur

d-b Asks: WindowServer and kerneltask using a lot of CPU in Big Sur
I have seen these two questions

WindowServer high CPU usage, spikes when moving cursor on M1 MacBook Big Sur

MacBook Pro – High CPU Under Low Workload

and I have the same problem with WindowServer on both a Macbook Pro 16″ and an Macbook Air 2020, but I also have problems with kernel_task.

According to the script here Uptime since boot excluding sleep for osx yosemite? my Air’s total awake time since last restart is 1 day, 22:07:19.374478 (uptime returns 9 days, 13:59, 5 users, load averages: 5,04 5,11 4,79).

Looking in Activity Monitor, WindowServer has used 42h05m since last restart (since the awake time is 46 hours, that is over 90 % on average) while kernel_task 14h19m ≈ 31 % (I will update this question with corresponding number for my MBP later on).

I mostly use this machine for web browsing and office tasks. These numbers are completely unreasonable! The computer is updated and reasonably “clean”. Since I have the same problem on my other machine I don’t think it is anything specific to this setup.

The only slightly odd usage is that I use Firefox – a well known resource hog – and it is hard to test if Firefox is the culprit since I need to use it 80-90 % of the time. A different browser isn’t really an option.

Any ideas what might be going on here?

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