Mastering Embedded Linux Programming - Second Edition

Fairness versus determinism

I have grouped the scheduling policies into categories of time-shared and real-time. Time-shared policies are based on the principal of fairness. They are designed to make sure that each thread gets a fair amount of processor time and that no thread can hog the system. If a thread runs for too long, it is put to the back of the queue so that others can have a go. At the same time, a fairness policy needs to adjust to threads that are doing a lot of work and give them the resources to get the job done. Time-shared scheduling is good because of the way it automatically adjusts to a wide range of workloads.

On the other hand, if you have a real-time program, fairness is not helpful. Instead, you then want a policy ...