Strange CPU usage in Xcode Activity Monitor

Question

This is a bit strange. When I execute the same app without changing anything in my code (just clicking "Record" in the Activity Monitor Instrument), I will get varying CPU on different runs - and it always varies by 10%.

This isn't switching back and forth in any systematic way, so my app can run at 30% CPU or 40% CPU (allowing the CPU to reach an equilibrium after a few seconds of startup).

What's causing this if nothing is changed in my code. Is it due to internal processes on the device?

EDIT:

Also, I don't retain any information or to my knowledge use any time varying functions (apart from the seed in some random functions...)

Answer 1

I think, CPU % will vary a little, for each execution.

The application should be executed for say 10 times, and the average CPU % should be considered as its actual load.