Best Case Response Time Analysis for Improved Schedulability Analysis of Distributed Real-Time Tasks

In distributed real-time systems, a task activated periodically by the completion of its preceding task can be modeled as a periodic task with activation jitter. An activation jitter of a task is defined as the difference between the worst case and best case response times of its preceding task. Because current approaches assume that the best case response time is zero or much smaller than the actual one, the activation jitter and the worst case response time of lower priority tasks are overestimated. This paper proposes a new analysis technique to calculate the best case response time more precisely and to reduce the activation jitter bounds. The proposed technique aims to find the relative phase between tasks to obtain the best case response time. The precise analysis of the best case response time can reduce the worst case response time of other tasks and increase the schedulability. The simulation results show that the proposed analysis significantly improves the estimation of the best case and worst case response times, respectively.