Spontaneous Reload Cache: Mimicking a Larger Cache with Minimal Hardware Requirement

Abstract

In modern processor systems, on-chip Last Level Caches (LLCs) are used to bridge the speed gap between CPUs and off-chip memory. In recent years, the LRU policy effectiveness in low level caches has been questioned. A significant amount of recent work has explored the design space of replacement policies for CPUs' low level cache systems, and proposed a variety of replacement policies. All these pieces of work are based on the traditional idea of a conventional passive cache, which triggers memory accesses exclusively when there is a cache miss. Such passive cache systems have a theoretical performance upper bound, which is represented by Optimal Algorithm. In this work, we introduce a novel cache system called Spontaneous Reload Cache (SR-Cache). Contrary to passive caches, no matter whether a cache access is a hit or miss, an SR-Cache can actively load or reload an off-chip data block which is predicted to be used in the near future and evict the data block which has the lowest probability to be reused soon. We show that, with minimal hardware overhead, SR-Cache can achieve much better performance than conventional passive caches.