An efficient lock-aware transactional memory implementation

  • Authors:

  • Justin E. Gottschlich;Jeremy G. Siek;Manish Vachharajani;Dwight Y. Winkler;Daniel A. Connors

  • Affiliations:

  • University of Colorado at Boulder;University of Colorado at Boulder;University of Colorado at Boulder;Nodeka, LLC;Colorado State University

  • Venue:
  • Proceedings of the 4th workshop on the Implementation, Compilation, Optimization of Object-Oriented Languages and Programming Systems
  • Year:
  • 2009

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Abstract

Transactional memory (TM) is an emerging concurrency control mechanism that provides a simple and composable programming model. Unfortunately, transactions violate the semantics of mutual exclusion locks when they execute concurrently. Due to the prevalence of locks, transactions must be made lock-aware enabling them to correctly interoperate with locks. We present a lock-aware transactional memory (LATM) system that employs a unique communication method using local knowledge of locks coupled with granularity-based policies. Our system allows higher concurrent throughput than prior systems because it only prevents truly conflicting critical sections from executing concurrently. Furthermore, our system relaxes the prior requirement of transaction isolation when executing conflicting transactional critical sections and instead runs these transactions as irrevocable, improving transaction concurrency. We demonstrate our performance improvements mathematically and empirically. Our system also advances LATM research in terms of program consistency. This is achieved by detecting potential deadlocks at run-time and aborting the programs that contain them. Prior systems break deadlocks, which reveal partially executed critical sections to other threads, thereby violating mutual exclusion. Because our system disallows deadlocks, it does not suffer from mutual exclusion violations, improving program consistency.