DSVM consistency protocols for nested object transactions
In this dissertation, we consider a distributed shared virtual memory (DSVM) system that allows multiple concurrent nested object transactions to make transactional updates to the shared object space from different nodes across a network. To maintain correctness, the multiple copies of any object which are "cached" in the nodes' memories must be kept consistent. This dissertation presents a new memory consistency protocol, lazy object transactional entry consistency (LOTEC), that has lower communication requirements in an object-based software DSVM system, and can consequently achieve higher performance. LOTEC achieves this reduction in communication by deferring the transfer of an object's updated pages across the network until those pages are referenced by an acquiring transaction. Further, it is compatible with a newly developed concurrency control protocol, nested object two-phase locking. We show the correctness of the developed protocols and then evaluate the performance of a simulated DSVM system using LOTEC by comparing it with two other DSVM consistency protocols (object transactional entry consistency (OTEC) and conservative object transactional entry consistency (COTEC)) which are also described in the dissertation. The simulation results indicate that LOTEC will have the best performance in the described object-based DSVM system.