System-level Synthesis of Hard Real-Time Application Specific Systems

We present a new, system-level approach for the synthesis of multi-task hard real-time applications off-the-shelf processors. The goal is to select a set of processors with minimal cost while satisfying timing constraints. In our approach there are three design phases: resource allocation, assignment (partitioning), and scheduling. With the observation that the resource allocation is a search for a set of processors which requires the minimum cost, we adopted A* search based technique. For the assignment we use a variation of the forcedirected optimization technique to determine the effect of assigning a task onto a processor. The final scheduling of hard-real time tasks is done by our scheduler based on the Earliest Deadline First (EDF) scheduling. Our task-level scheduler is a unique modification of the EDF in that we applied the force-directed scheduling methodology to address the situations where the EDF is not optimal. The experimental results on a variety of examples show that this approach is highly effective on a variety of examples. 1.0 Introduction 1.1 Motivation Real-time systems can be defined as those systems in which the proper functioning of the implementation depends not only on the logical correctness of the computation, but also on the time at which the results are produced [Ram94]. Classical examples include automobile and airplane monitoring and control systems, a variety of command and control systems, and process control systems. The number of modern real-time systems has been growing exponentially, mainly in connection with wireless and broadband communication. Multimedia, video-on-demand, interactive television, and remote sensor security control are among the most popular applications today and form a fast growing segment of the