Schedulability Test for Soft Real-Time Systems under Multiprocessor   Environment by using an Earliest Deadline First Scheduling Algorithm
  This paper deals with the study of Earliest Deadline First (EDF) which is an optimal scheduling algorithm for uniprocessor real time systems use for scheduling the periodic task in soft real-time multiprocessor systems. In hard real-time systems, a significant disparity exists EDF-based schemes and RMA scheduling (which is the only known way of optimally scheduling recurrent real-time tasks on multiprocessors): on M processors, all known EDF variants have utilization-based schedulability bounds of approximately M/2, while RMA algorithms can fully utilize all processors. This is unfortunate because EDF based algorithms entail lower scheduling and task migration overheads. In work on hard real-time systems, it has been shown that this disparity in Schedulability can be lessened by placing caps on per task utilizations. Our main contribution is a new EDF based scheme that ensures bounded deadline tardiness. In this scheme, per-task utilizations must be focused,but overall utilization need not be stricted. Our scheme should enable a wide range of soft real-time applications to be scheduled with no constraints on total utilization. Also propose techniques and heuristics that can be used to reduce tardiness as well as increase the efficiency of task. 
Jagbeer Singh, Satyendra Prasad Singh
cs.OS