Toward high performance nonblocking software transactional memory

Substantial advances in STM performance in recent years have mostly focused on blocking systems. We describe our work inte-grating the most important techniques and optimizations emerging from the recent work on blocking STMs into several variants of a nonblocking STM. In particular, our design is based on the philosophy of keep-ing the common, contention free execution path as simple (conse-quently fast) as possible, while resorting to the more expensive data displacement and metadata management only in situations where transactions have problems making forward progress. We employ novel ownership “stealing ” and metadata management techniques in our nonblocking STM to enable several recent blocking STM optimizations such as timestamp-based validation and ownership release via store instructions, all leading to a more streamlined and efficient fast path. We present an undo log (eager versioning) vari-ant of our STM, as well as two redo log (lazy versioning) variants, the latter of which are based on the two ownership acquisition tech-niques (namely eager and lazy) for writes made by transactions. Experimental results show that our efforts have improved the performance of nonblocking STMs up to the level of being com-petitive with the state-of-the-art blocking STMs such as TL2