[kqr]

I agree. It's not even about efficiently utilising resources. If we process things in timeslices that immediately kills any bad effects variability has on the workload. Small jobs go fast even if a big job happened to arrive in front of it.

(Of course, it's still a tradeoff between context switching overhead and the magnitude of the variability, but fundamentally even a tiny level of timeslicing can be a huge improvement.)