Coupling compiler-enabled and conventional memory accessing for energy efficiency

Abstract

This article presents Cool-Mem, a family of memory system architectures that integrate conventional memory system mechanisms, energy-aware address translation, and compiler-enabled cache disambiguation techniques, to reduce energy consumption in general-purpose architectures. The solutions provided in this article leverage on interlayer tradeoffs between architecture, compiler, and operating system layers. Cool-Mem achieves power reduction by statically matching memory operations with energy-efficient cache and virtual memory access mechanisms. It combines statically speculative cache access modes, a dynamic content addressable memory-based (CAM-based) Tag-Cache used as backup for statically mispredicted accesses, different conventional multilevel associative cache organizations, embedded protection checking along all cache access mechanisms, as well as architectural organizations to reduce the power consumed by address translation in virtual memory. Because it is based on speculative static information, a superset of the predictable program information available at compile-time, our approach removes the burden of provable correctness in compiler analysis passes that extract static information. This makes Cool-Mem highly practical, applicable for large and complex applications, without having any limitations due to complexity issues in our compiler passes or the presence of precompiled static libraries. Based on extensive evaluation, for both SPEC2000 and Mediabench applications, we obtain from 6% to 19% total energy savings in the processor, with performance ranging from 1.5% degradation to 6% improvement, for the applications studied. We have also compared Cool-Mem to several prior arts and have found Cool-Mem to perform better in almost all cases.