Locking with different granularities for reads and writes in an MVM system

Investigates the use of a multi-view virtual memory (MVM) in providing efficient locking services for transaction processing or database systems. The locking granularity is customizable by applications and, furthermore, the locking granularities for read and write operations may differ. The system provides for the enforcement of access control protocols on units of a memory region through finite state machine (FSM) specification. The data units can vary in size from one memory region to another. Threads executing transactions do not explicitly request locks on data items-they simply access the data items, while locking is represented through state transitions and is performed automatically. Only when a thread is suspended are the state changes communicated to the software lock manager. The context switching overhead is thus reduced. Synchronization of threads is possible within a single task or across tasks. Any synchronization protocol that can be represented by an FSM is supported by the MVM system. This paper describes how MVM supports sophisticated locking in which the locking granularities for read and write operations differ. The benefits gained using such locking, which are expressed in terms of throughput, are investigated using a simulation study