EcoTM: Conflict-Aware Economical Unbounded Hardware Transactional Memory

Transactional Memory (TM) is a promising paradigm for parallel programming. TM allows a thread to make a series of memory accesses as a single, atomic, transaction, while avoiding deadlocks, livelocks, and other problems commonly associated with lock-based programming. In this paper we explore Hardware support for TM (HTM). In particular, we explore how HTM can efficiently support transactions of nearly unlimited size. For this purpose we propose EcoTM, an economical unbounded HTM that improves the efficiency of conflict detection between very large transactions by activating conflict-detection logic only for potentially-conflicting locations: shared and speculatively modified. EcoTM detects the potentially-conflicting locations automatically, without any program annotations. We evaluate EcoTM performance by comparing it with ideal-lazy HTM, unbounded eager HTM with perfect signatures, and LogTM-SE. Our evaluations show that EcoTM has similar performance as the ideal-lazy HTM, 8.8% better than the eager-perfect HTM, and over 35.7% better than LogTM-SE, on the average.