The yielding-first rate-monotonic scheduling approach and its efficiency assessment

In real-time (RT) computing systems, a service function execution including an output action is typically subject to a deadline. Scheduling algorithms play a significant role in the design of such systems. They are the major factor in determining the execution safety, i.e., the possibility of always executing control service functions without missing deadlines in a given execution engine possessing a limited set of execution resources. The rate-monotonic (RM) fixed-priority scheduling approach is one of the oldest scheduling approaches devised for use in RT computing systems [1–3]. It can be used effectively in a narrow class of RT application situations. In this paper, we attempt to add some to the knowledge-base related to the RM approach. The essence of the RM approach is: (E1) To structure the RT application software in the form of a set of cyclic fixed-priority processes, each iterating the sequence of receiving a service request signal coming from a controlled device or timer and executing a control service function; (E2) To make the priority number associated with each process to be either inversely proportional to the minimum request interval (MRI), i.e., the minimum interval between two successive arrivals of service request signals, or proportional to the maximum request rate which is the maximum rate of arrivals of service request signals, which is also called the maximum service rate; and (E3) To select the highest-priority process at every selection point.