A scalable scheduling algorithm for real-time distributed systems

Scheduling real time tasks in a distributed memory multiprocessor is characterized as sequencing a set of tasks and assigning them to processors of the architecture. Real time systems research has extensively investigated the sequencing dimension of the scheduling problem by extending uniprocessor scheduling techniques to more complex architectures. We introduce a technique that uses an assignment oriented representation to dynamically schedule real time tasks on the processors of the system. The technique we propose, automatically controls and allocates the scheduling time, in order to minimize deadline violation of real time tasks, due to the scheduling overhead. We evaluate this technique in the context of scheduling real time transactions in a distributed database application which we implemented on an Intel Paragon distributed memory multiprocessor. In this implementation, we compared the performance of our algorithm with another dynamic algorithm that uses a sequence oriented representation. The results show interesting performance trade-offs among the candidate algorithms and validate our conjectures about scalability performance limitations of sequence oriented representations. The results also show the effect of the mechanisms that our technique uses to control and allocate scheduling time