Design of a new OFTM algorithm towards abort-free execution

Abstract

The Software Transactional Memory (STM) is a promising alternative to lock based concurrency control. Three well studied progress conditions for implementing STM are, wait-freedom, lock-freedom and obstruction-freedom. The wait-freedom is the strongest progress property. It rules out the occurrence of deadlock and starvation but impose too much implementation overhead. The obstruction freedom property is weaker than wait-freedom and lock-freedom. Obstruction Free Transactional Memory (OFTM) is simpler to implement, rules out the occurrence of deadlock and has faster performance in absence of contention. A transaction T k that opens an object, say X, for updating may be in the active state even after completion of update operation on X. Hence, object X cannot be accessed by any other transaction as the current transaction T k is still active. At this point, if another transaction T m wants to acquire object X at this point (for read/write), either T k needs to be aborted or T m must wait till T k finishes. Both of these approaches are detrimental for the performance of the system. Besides, OFTM does not allow T m to wait for the completion of T k. In this paper, a new OFTM implementation methodology has been proposed to allow the second transaction T m to proceed immediately without affecting the execution of the first transaction T k. The proposed approach yields higher throughput as compared to existing OFTM approaches that calls for aborting transactions. © 2013 Springer-Verlag Berlin Heidelberg.