CSR: Small: Nested Distributed Software Transactional Memory: Protocols, Mechanisms, and Java Package

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In this project, protocols, mechanisms, and a Java implementation of nested distributed transactional memory (TM) are developed. Distributed TM promises to alleviate the programmability, scalability, and performance challenges of lock-based distributed concurrency control. Emerging distributed TM implementations export a simple programming interface that precludes locks and are yielding performance comparable to, or better than lock-based distributed concurrency control. Nesting is essential to distributed TM for composability, functionality, fault-management, and performance. The project is developing protocols and mechanisms to support closed and open nesting in distributed TM. Closed nesting allows a nested transaction to be aborted without aborting the parent transaction, but not vice versa. Open nesting allows a parent transaction to be aborted without aborting the nested transaction, and vice versa, permitting greater concurrency. To support these nesting models, the project is developing distributed transactional conflict resolution protocols, distributed cache coherence protocols, and mechanisms for transparently executing compensating transactions to undo the effects of committed transactions. The project is implementing these techniques in the open-source, HyFlow distributed TM Java package (hyflow.org). The project is also transitioning this technology (techniques and HyFlow implementation) to US Navy's Aegis Combat System, which uses distributed concurrency control. Additionally, the project's results are being incorporated into advanced graduate courses at Virginia Tech that includes students at Blacksburg, VA, scientists and engineers at US Naval Surface Warfare Center Dahlgren Division (NSWCDD), VA (through Virginia Tech's graduate outreach program at NSWCDD), and students in the Middle East and North Africa through Virginia Tech's VT-MENA program at Egypt.