system
Given the following post, respond as if you're commenting on Reddit:
human
Why isnt CPU usage always 100% if the CPU is always running some prrocess?

Ive read that the CPU is always running exactly one process. Even if the CPU runs the idle process its still busy waiting and executing instructions. Than why isnt CPU usage always maxed out?
gpt
If you mean the CPU usage percentage reported by the operating system, it only makes sense to exclude the idle process from the total percentage. After all, the purpose of the CPU usage figure is to tell how much of total capacity is, at least in theory, currently being used. The idle process would only take up the fraction that's not being used by any other process.

With that said, nowadays when the CPU is idle, it's not actually running a busy-waiting idle process. The OS or the hardware itself will set the CPU in a power-saving mode that may turn off parts of the CPU. So, with any modern hardware, it's not actually true that the CPU would always be executing something.