Current Results on EDZL Scheduling for Multiprocessor Real-Time Systems

Many optimal uniprocessor schedulers, such as earliest deadline first (EDF) and rate monotonic (RM), do not have a good schedulability bound on multiprocessor systems. In this paper, we study an on-line algorithm earliest deadline first until Zero laxity (EDZL) for multiprocessor systems. A set of tasks scheduled by EDZL is scheduled using EDF until a job experiences a zero laxity. To avoid the job from missing its deadline, the priority of the job is immediately promoted to the highest priority. We derive the schedulability bound of 3/2+_umax-1/2 for two-processor systems, where u_max is the maximum utilization of an individual task in the given task set. We also discuss the best known upper bound and lower bound on EDZL schedulability conditions.