Investigation of hardware transactional memory

Abstract

Hardware transactional memory is a new method of optimistic concurrency control that can be used to solve the synchronization problem in multicore software. It is a promising solution due to its simple semantics and good performance relative to traditional approaches. Before we can incorporate this nascent technology into high-performing concurrent programs, it is necessary to investigate the physical capacity constraints and performance characteristics of hardware transactions in order to better inform programmers of their abilities and limitations. Our investigation involves the first empirical study of the "capacity envelope" of HTM in Intel's Haswell and IBM's Power8 architectures. We additionally survey how contention parameters, such as transaction size or write ratio, affect HTM performance and we capture these trends in a regression model for predicting the throughput of HTM-enabled concurrent programs. Through our investigation, we aim to provide what we believe is a much needed understanding of the extent to which one can use HTM to replace locks.