Compiler-Directed Cache Assist Adaptivity

The performance of a traditional cache memory hierarchy can be improved by utilizing mechanisms such as a victim cache or a stream bu er (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 bu er 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 e ect 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. 2