R-EDF: a reservation-based EDF scheduling algorithm for multiple multimedia task classes

Multimedia applications became an integral part of the ubiquitous computing environment in general-purpose systems. However, current general-purpose operating systems cannot effectively support their soft real-time requirements. This paper presents a reservation-based preemptive earliest deadline first (R-EDF) algorithm to provide a predictable scheduling framework in an open shared environment. The major contributions of R-EDF are: it delivers timing guarantees to four soft real-time task classes such as period class with constant and various processing time, aperiodic class and event-based class; it provides starvation protection for best-effort tasks; it provides overrun protection and handling so that an overrun task will not cause other tasks to miss deadlines and will finish its work within an acceptable and predictable time bound; and it allows optimistic reservation and incurs low overhead cost for reservation and admission control. Our experimental results show the low overhead and correctness of R-EDF even when there is resource contention.