Cache Exclusivity and Sharing

Abstract

A problem on multicore systems is cache sharing, where the cache occupancy of a program depends on the cache usage of peer programs. Exclusive cache hierarchy as used on AMD processors is an effective solution to allow processor cores to have a large private cache while still benefitting from shared cache. The shared cache stores the “victims” (i.e., data evicted from private caches). The performance depends on how victims of co-run programs interact in shared cache. This article presents a new metric called the victim footprint (VFP). It is measured once per program in its solo execution and can then be combined to compute the performance of any exclusive cache hierarchy, replacing parallel testing with theoretical analysis. The work evaluates the VFP by using it to analyze cache sharing by parallel mixes of sequential programs, comparing the accuracy of the theory to hardware counter results, and measuring the benefit of exclusivity-aware analysis and optimization.