The Efficacy of Commutativity-based Semantic Locking in Real-world Applications

While the dominant approach to persistent storage in practice is to use a relational DBMS, there are some specialist applications that rely on object stores. The performance of these applications depends heavily on the efficiency of the object store’s concurrency control mechanism. Today’s predominant concurrency control mechanism is strict two-phase object locking. In the 80s, an interesting alternative was developed: commutativity-based semantic locking. In theory, it can outperform traditional locking schemes in certain scenarios with appropriate commutativity potential. However, such scenarios are not easily identifiable; hence semantic locking never became popular. In this paper, we study the real-world performance potential of different locking strategies in an industrial application from the telecommunications sector. We compare object-based locking, field-based locking, and commutativity-based semantic locking. We found that semantic locking performs equally to, but no better than, object and field locking in reasonable mixes of real-world transactions, and that it outperforms these locking levels in a contrived mix with high commutativity potential. To the best of our knowledge, this is the first experimental study of semantic locking in a real-world application. ——————————  ——————————