An Optimal Scheduling Algorithm for Soft Aperiodic Tasks

The problem of hybrid scheduling of hard period task and soft aperiodic task is important part of the research of real-time scheduling. To analysis the idle and movable time of period task set scheduled by earliest deadline first scheduling algorithm, two definitions scheduling and converse scheduling are given. These two definitions are used to calculate the max movable time of period task set. Using the max movable time, an algorithm named idle stealing algorithm （ISA） is given to decrease the response time of aperiodic task. ISA makes full use of the max movable time of period task set. It can largely decrease the response time of aperiodic tasks while guaranteeing the deadline of period tasks. The ISA algorithm provides the shortest response time of aperiodic task and is proved to be optimal by experiments.