Question

Compare Earliest-Deadline First (EDF) scheduling against Rate-Monotonic (RM) scheduling. Now, consider an overloaded system, i.e., the total CPU utilization of all tasks is higher than 100%. In your opinion, between EDF and RM, which one is better, and from what perspective?

Answer 1

The Earliest Deadline First is a Dynamic Priority scheduling Algorithm in which dynamically the processes are placed in the queue by the RT OS. Whereas Rate Monotonic Algorithm uses Fixed Priority Scheduling Algorithm.

EDF is used for scheduling periodic as well as aperiodic tasks because,it has no assumption on periodicity of the tasks. But in the Rate Monotonic Algorithm, the priority of the task is inversely proportional to the period, which means scheduling depends on period of the task.

Now, consider an overloaded system......, When the system is overloaded, the set of processes that will miss deadline is largely unpredictable.

For such a scenario fixed priority scheduling i.e, Rate Monotonic Algorithm is the best.

With fixed priorities, it is easy to predict that overload conditions will cause the low-priority processes to miss deadlines, while the highest priority process will still meet its deadline.