Scheduling parallelizable jobs on multiprocessors

The effect of parallel execution on the complexity of scheduling hard real-time jobs on multiprocessors is analyzed. Studied is the scheduling problem in which a job may be parallelized and executed on any number of processors concurrently. In hard real-time systems, each job must be completed before a deadline. Parallelization gives a scheduler the flexibility to allocate more processors to a job whose deadline is near. Unfortunately, with this flexibility some of the multiprocessor scheduling problems are very difficult. The NP-hardness of scheduling parallelizable jobs where each job has a fixed priority is proved. A heuristic algorithm is proposed for finding an approximate job partition on two processors. Simulation results show that the heuristic algorithm usually has a very good performance.