An EDF-based restricted-migration scheduling algorithm for multiprocessor soft real-time systems

There has been much recent interest in the use of the earliest-deadline-first (EDF) algorithm for scheduling soft real-time sporadic task systems on identical multiprocessors. In hard real-time systems, a significant disparity exists between EDF-based schemes and Pfair scheduling: on M processors, the worst-case schedulable utilization for all known EDF variants is approximately M/2, whereas it is M for optimal Pfair algorithms. This is unfortunate because EDF-based algorithms entail lower scheduling and task-migration overheads. However, such a disparity in schedulability can be alleviated by easing the requirement that all deadlines be met, which may be sufficient for soft real-time systems. In particular, in recent work, we have shown that if task migrations are not restricted, then EDF (i.e., global EDF) can ensure bounded tardiness for a sporadic task system with no restrictions on total utilization. Unrestricted task migrations in global EDF may be unappealing for some systems, ...

• Type: Journal
• Year: 2008
• Where: RTS
• Authors: James H. Anderson, Vasile Bud, UmaMaheswari C. Devi
• Keywords: Global Edf, RTS 2008, Sporadic Task, Task Migrations