I just found #cpulimit, which nicely (haha) complements #nice. nice just makes your process get out of the way if something else has a higher priority. cpulimit makes it just get out of the way, so if I start something like #ffmpeg going just before bed time the machine won't run the noisy fans but will still have the job done by the time I wake up. It works by throttling a process with SIGSTOP/SIGCONT a bit like how #tcpnice sabotages network connections. https://github.com/opsengine/cpulimit