Minimizing Scheduling Overhead In LRE-TL Real-Time Multiprocessor Scheduling Algorithm

In this paper, we present a modification of Local Remaining Execution-Time and Local time domain (LRE-TL) real-time multiprocessor scheduling algorithm, aimed at reducing the scheduling overhead in terms of task migrations. LRE-TL achieves optimality by employing the fairness rule at the end of each time slice in a fluid schedule model. LRE-TL makes scheduling decisions using two scheduling events. The Bottom (B) event, which occurs when a task consumes its local utilization thus; it has to be preempted in order to resume the execution of another task, if any, or to idle the processor if none exist. The Critical (C) event occurs when a task consumes its local laxity which means that the task cannot wait any more and has to be scheduled for execution immediately otherwise, it will miss its deadline. Event C always results in a task migration. We have modified the initialization procedure of LRE-TL to make sure that tasks which have higher probability of firing a C event will always be considered for execution first. This will ensure that the number of C events will always be at the minimum; thereby reducing the number of task migrations.