Sufficient condition for real-time non-preemptive scheduling of interactive multimedia tasks

In many fields, non-preemptive real-time scheduling of a set of periodic tasks with different release times is very important if not even necessary. The number and characteristics of tasks may vary during time, thus imposing to re-evaluate the task schedulability over time. In this paper we propose an efficient sufficient schedulability condition, and we analytically show that if this bound is satisfied, the tasks are real-time schedulable under the non-preemptive Earliest Deadline First and Rate Monotonic policies. We experimentally analyse, by simulation, the bound and show that in practical cases occurring in Multimedia processing its validity remains significant for a very large range of CPU utilisation factors. In the same way we show by simulation that the gap of the proposed condition to the sufficient and necessary condition is negligible if the difference between the periods of periodic tasks is small. Finally, we give a graphical interpretation of the proposed bound and some application examples.