Consistency Check through O-GEHL Predictors

Abstract

Transactional Memory (TM) is a promising paradigm to facilitate parallel programming for multicore processors. In Software implementation of TMs (STMs), transactions rely on a global clock to maintain consistency of transactional data. While this method is simple to implement, it results in significant timing overhead if transactions commit frequently. The alternative approach is Thread Local Clock (TLC) which exploits decentralized local variables to maintain consistency in transactions. However, TLC may increase false aborts and degrade performance of STMs. In this paper, we introduce Adaptive Clock (AC) which dynamically selects one of the two validation techniques based on probability of conflicts. AC is a speculative approach and relies on O-GEHL predictors to speculate future conflicts. We have incorporated AC into TL2 and compared the performance of the new implementation with the original STM using Stamp v0.9.10 benchmark suite. Our results reveal that AC is effective and improves performance of transactional applications up to 33%.