Cache misses in small, limited-associativity primary caches very often replace live cache blocks, given the dominance of capacity and conflict misses. Towards motivating novel cache organizations, we study the comparative characteristics of the virtual memory address pairs involved in typical primary-cache contention (block replacements) for the SPEC2000 integer benchmarks. We focus on the cache tag bits, and results show that (i) often just a few tag bits differ between contending addresses, and (ii) accesses to certain segments or page groups of the virtual address space (i.e. certain tag-bit groups) contend frequently. Cacheconscious virtual address space allocation can further reduce the number of conflicting tag bits. We mention two directions for exploiting such page-level contention patterns to improve cache cost and performance.
Siddhartha V. Tambat, Sriram Vajapeyam