Run-time compaction of FPGA designs

Abstract

Controllers for dynamically reconfigurable FPGAs that are capable of supporting multiple independent tasks simultaneously need to be able to place designs at run-time when the sequence or geometry of designs is not known in advance. As tasks arrive and depart the available cells become fragmented, thereby reducing the controller's ability to place new tasks. The response times of tasks and the utilization of the FPGA consequently suffer. In this paper, we describe and assess a task compaction heuristic that alleviates the problems of external fragmentation by exploiting partial reconfiguration. We identify a region of the chip that can satisfy the next request after the designs occupying the region have been moved. The approach is simple and platform independent. We show by simulation that for a wide range of task sizes and configuration delays, the response of overloaded systems can be improved significantly.