Victim management in a cache hierarchy

Abstract

We investigate directions for exploiting what might be termed pattern locality in a cache hierarchy, based on recording cache discards or victims. An advantage of storing discard decisions is the reduced duplication of pertinent information, as well as the maintenance of information on the current location of discarded lines. Typical caches are designed to exploit combinations of temporal and spatial locality. Temporal locality, the likelihood that recently referenced data will be referenced again, is exploited by LRU-like algorithms. Spatial locality is the property that causes larger cache lines to yield improved miss ratios. Here we consider the exploitation of pattern locality--the property that lines accessed in temporal proximity tend to be re-referenced together. We describe some new cache structures including pattern-recording features, along with their miss ratio and transfer traffic performance as determined via simulations on traces drawn from several benchmark applications. We show that pattern locality information, based on discard statistics, can be useful in enhancing the quality of prefetch decisions.