Design and performance evaluation of a cache assist to implement selective caching

Conventional cache architectures exploit locality, but do so rather blindly. By forcing all references through a single structure, the cache´s effectiveness on many references is reduced. This paper presents a cache assist namely the annex cache which implements a selective caching scheme. Except for filling a main cache at cold start, all entries come to the cache via the annex cache. Items referenced only rarely will be excluded from the main cache, eliminating several conflict misses. The basic premise is that an item deserves to be in the main cache only if it can prove its right to exist in the main cache by demonstrating locality. The annex cache combines the features of Jouppi´s (1990) victim caches and McFarling´s (1992) cache exclusion schemes. Extensive simulation studies for annex and victim caches using a variety of SPEC programs are presented in the paper. Annex caches were observed to be significantly better than conventional caches, better than victim caches in certain cases, and comparable to victim caches in other cases