Windows is very bad at this. If you try to change priority of a task in Task Manager, you literally get a warning that it might make your system unstable. And they don’t prioritize responsiveness of the GUI so any time a virus scan starts or Windows Update kicks off, most computers feel extremely slow. Those should both always be background tasks that should only be using spare cycles only.

Higher CPU usage is good. It means it’s not IO bound and it will finish sooner. The problem comes when your CPU scheduler doesn’t give priority to keeping the system responsive.