Achieving efficient packet-based memory system by exploiting correlation of memory requests

Abstract

Packet-based interface is a trend for future memory system to alleviate memory capacity and bandwidth bottlenecks. On the other hand fine-grained memory access has been proven to efficiently reduce memory power. However leveraging both these two technologies will result in high packet overhead, because previous implementations of packet-based interface all adopt a simple design that a single packet is dedicated to a single request (SPSR). In this paper, we propose three optimizations to overcome the problem by exploiting correlations of memory requests. First, we propose a novel single packet multiple requests (SPMR) interface that encapsulates multiple requests into a packet to share packet header and tail. Second, we propose an adaptive address compression mechanism within a packet by adopting a base-difference algorithm. Third, we propose a mechanism to merge multiple memory requests with continuous access addresses into a single request before packing. By this way, the granularity constraint of cache line size is broken to enable efficiently row buffer scheduling. The experimental results show that, for certain memory-intensive workloads, the optimizations can effectively reduce packet overhead by about 53.9% and improve system performance by about 63.6% in average.