When evaluating CPU usage of an in development plugin on PC or Intel Mac I usually load a single instance of said plugin in reaper and check the CPU percentage at the bottom of the container window.
I also make sure the CPU is running at its maximum clock speed beforehand by running a CPU intensive process in the background (typically a simple batch or perl infinite loop).
This works fairly well on x86 CPUs, with consistent readings and lower CPU usage than without the background loop, but I was not able to use the same strategy on the M1 chip.
It looks like the high-performance / high-efficiency core dichotomy is responsible for this, the loop running on a high-performance core while the plugin is running on a high-efficiency on.
I might well be missing something here, but the end result is that CPU usage is unchanged with or without the background loop, is not very stable, and is also notably higher than expected (read higher than the Intel counterpart).
Any idea on how to determine CPU usage on M1 chips?