Experimental analysis of timing validation methods for distributed real-time systems

Scheduling jobs dynamically on processors is likely to achieve better performance in multiprocessor and distributed real-time systems. Exhaustive methods for determining whether all jobs complete by their deadlines, in systems that use modern priority-driven scheduling strategies, are often infeasible or unreliable since the execution time of each job may vary. We previously published research results on finding worst-case bounds and efficient algorithms for validating systems in which independent jobs have arbitrary release times and deadlines, and are scheduled on processors dynamically in a priority-driven manner. An efficient method has been proposed to determine how late the completion times of jobs can be in dynamic systems where the jobs are preemptable and nonmigratable. This paper further presents the performance characteristics of the proposed methods, and shows its soundness by providing extensive simulation results. The worst-case completion times of jobs obtained with the proposed methods are compared with the values by simulations under different workload characteristics. The simulation results show that the proposed algorithm performs considerably well for diverse workloads. Considering the previous work showed the unlikelihood of finding tighter bounds than the one given in the paper, the simulation results indicate that the proposed methods effectively constitute a theoretical basis needed for a comprehensive validation strategy that is capable of dealing with dynamic distributed real-time systems.