Online Schedulability Tests for Real-Time Systems

Modern real-time systems have to be adaptable and flexible to deal with non-periodic events, requiring a means of checking for schedulability during execution time. Thus, online schedulability tests are a fundamental building block in the design of such systems. Usually, when such tests are carried out at time t they either consider or not future events that occur after t. Those that take such events into consideration are based on previously derived offline scheduling. Otherwise, they focus only on the jobs that are active at t. Unlike these usual approaches, we describe in this paper two online tests that verify schedulability within a given time interval [t, t′) so that future event occurrences are considered but bounded within the interval. The tests are proved correct and are evaluated by simulation.