A Real-Time Multichannel Memory Controller and Optimal Mapping of Memory Clients to Memory Channels

Abstract

Ever-increasing demands for main memory bandwidth and memory speed/power tradeoff led to the introduction of memories with multiple memory channels, such as Wide IO DRAM. Efficient utilization of a multichannel memory as a shared resource in multiprocessor real-time systems depends on mapping of the memory clients to the memory channels according to their requirements on latency, bandwidth, communication, and memory capacity. However, there is currently no real-time memory controller for multichannel memories, and there is no methodology to optimally configure multichannel memories in real-time systems. As a first work toward this direction, we present two main contributions in this article: (1) a configurable real-time multichannel memory controller architecture with a novel method for logical-to-physical address translation and (2) two design-time methods to map memory clients to the memory channels, one an optimal algorithm based on an integer programming formulation of the mapping problem, and the other a fast heuristic algorithm. We demonstrate the real-time guarantees on bandwidth and latency provided by our multichannel memory controller architecture by experimental evaluation. Furthermore, we compare the performance of the mapping problem formulation in a solver and the heuristic algorithm against two existing mapping algorithms in terms of computation time and mapping success ratio. We show that an optimal solution can be found in 2 hours using the solver and in less than 1 second with less than 7% mapping failure using the heuristic for realistically sized problems. Finally, we demonstrate configuring a Wide IO DRAM in a high-definition (HD) video and graphics processing system to emphasize the practical applicability and effectiveness of this work.