An open distributed real-time environment based on variable utilization server

This paper extends the environment for open distributed real-time systems [17], where hard or soft real-time applications may run concurrently with nonreal-time applications. We replace the top-level improved constant utilization server scheduler of the open system architecture in [17] with variable utilization server scheduler. The proposed open realtime environment in this paper allows tasks in each application to share local and global nonpreemptive resources, which accommodates a much broader spectrum of real-time applications. Additionally, the extended environment assigns CPU bandwidth to each server in a more flexible and more adaptive way. The evaluation results show the performance of the open system is also improved considerably.