PHyTM: Persistent Hybrid Transactional Memory

Processors with hardware support for transactional memory (HTM) are rapidly becoming commonplace, and processor manufacturers are currently working on implementing support for upcoming non-volatile memory (NVM) technologies. The combination of HTM and NVM promises to be a natural choice for in-memory database synchronization. However, limitations on the size of hardware transactions and the lack of progress guarantees by modern HTM implementations prevent some applications from obtaining the full benefit of hardware transactional memory. In this paper, we propose a persistent hybrid TM algorithm called PHyTM for systems that support NVM and HTM. PHyTM allows hardware assisted ACID transactions to execute concurrently with pure software transactions, which allows applications to gain the benefit of persistent HTM while simultaneously accommodating unbounded transactions (with a high degree of concurrency). Experimental simulations demonstrate that PHyTM is fast and scalable for realistic workloads.