Compiler–directed cache assist adaptivity

Abstract

The performance of a traditional cache memory hierarchy can be improved by utilizing mechanisms such as a victim cache or a stream buffer (cache assists). The amount of on–chip memory for cache assist is typically limited for technological reasons. In addition, the cache assist size is limited in order to maintain a fast access time. Performance gains from using a stream buffer or a victim cache, or a combination of the two, varies from program to program as well as within a program. Therefore, given a limited amount of cache assist memory, there is a need and a potential for “adaptivity” of the cache assists i. e., an ability to vary their relative size within the bounds of the cache assist memory size. We propose and study a compiler-driven adaptive cache assist organization and its effect on system performance. Several adaptivity mechanisms are proposed and investigated. The results show that a cache assist that is adaptive at loop level clearly improves the cache memory performance, has low overhead, and can be easily implemented.