Lightweight locking for main memory database systems

Locking is widely used as a concurrency control mechanism in database systems. As more OLTP databases are stored mostly or entirely in memory, transactional throughput is less and less limited by disk IO, and lock managers increas-ingly become performance bottlenecks. In this paper, we introduce very lightweight locking (VLL), an alternative approach to pessimistic concurrency control for main-memory database systems that avoids almost all overhead associated with traditional lock manager opera-tions. We also propose a protocol called selective contention analysis (SCA), which enables systems implementing VLL to achieve high transactional throughput under high con-tention workloads. We implement these protocols both in a traditional single-machine multi-core database server set-ting and in a distributed database where data is partitioned across many commodity machines in a shared-nothing clus-ter. Our experiments show that VLL dramatically reduces locking overhead and thereby increases transactional through-put in both settings. 1