Application Clustering Policies to Address System Fairness with Intel’s Cache Allocation Technology

Achieving system fairness is a major design concern in current multicore processors. Unfairness arises due to contention in the shared resources of the system, such as the LLC and main memory. To address this problem, many research works have proposed novel cache partitioning policies aimed at addressing system fairness without harming performance. Unfortunately, existing proposals targeting fairness require extra hardware which makes them impractical in commercial processors.Recent Intel Xeon processors feature Cache Allocation Technology (CAT), a hardware cache partitioning mechanism that can be controlled from userspace software and that allows to create partitions in the LLC and assign different groups of applications to them.In this paper we propose a family of clustering-based cache partitioning policies to address fairness in systems that feature Intel’s CAT. The proposal acts at two levels: applications showing similar amount of core stalls due to LLC accesses are first grouped into clusters, after which each cluster is given a number of ways using a simple mathematical model. To the best of our knowledge, this is the first attempt to address system fairness using the cache partitioning hardware in a real product. Results show that our best performing policy reduces system unfairness by up to 80% (39% on average) for 8-application workloads and by up to 45% (25% on average) for 12-application workloads compared to a non-partitioning approach.