Snapshot Isolation for Software Transactional Memory

Software transactional memory (STM) has been proposed to simplify the development and to increase the scalability of concurrent programs. One problem of existing STMs is that of having long-running read transactions co-exist with shorter update transactions. This problem is of practical importance and has so far not been addressed by other papers in this domain. We approach this problem by investigating the performance of a STM using snapshot isolation and a novel lazy multi-version snapshot algorithm to decrease the validation costs which can increase quadratically with the number of objects read in STMs with invisible reads. Our measurements demonstrate that snapshot isolation can increase throughput for workloads with long transactions. In comparison to other STMs with invisible reads, we can reduce the validation costs by using our lazy consistent snapshot algorithm.