CSMV: A Highly Scalable Multi-Versioned Software Transactional Memory for GPUs

GPUs have traditionally focused on streaming applications with regular parallelism. Over the last years, though, GPUs have also been successfully used to accelerate irregular applications in a number of application domains by using fine grained synchronization schemes. Unfortunately, fine-grained synchronization strategies are notoriously complex and error-prone. This has motivated the search for alternative paradigms aimed to simplify concurrent programming and, among these, Transactional Memory (TM) is probably one of the most prominent proposals. This paper introduces CSMV (Client Server Multiversioned), a multi-versioned Software TM (STM) for GPUs that adopts an innovative client-server design. By decoupling the execution of transactions from their commit process, CSMV provides two main benefits: (i) it enables the use of fast on chip memory to access the global metadata used to synchronize transaction (ii) it allows for implementing highly efficient collaborative commit procedures, tailored to take full advantage of the architectural characteristics of GPUs. Via an extensive experimental study, we show that CSMV achieves up to 3 orders of magnitude speed-ups with respect to state of the art STMs for GPUs and that it can accelerate by up to 20× irregular applications running on state of the art STMs for CPUs.