JANUS: exploiting parallelism via hindsight

This paper addresses the problem of reducing unnecessary conflicts in optimistic synchronization. Optimistic synchronization must ensure that any two concurrently executing transactions that commit are properly synchronized. Conflict detection is an approximate check for this condition. For efficiency, the traditional approach to conflict detection conservatively checks that the memory locations mutually accessed by two concurrent transactions are accessed only for reading. We present JANUS, a parallelization system that performs conflict detection by considering sequences of operations and their composite effect on the system’s state. This is done efficiently, such that the runtime overhead due to conflict detection is on a par with that of write-conflict-based detection. In certain common scenarios, this mode of refinement dramatically improves the precision of conflict detection, thereby reducing the number of false conflicts. Our empirical evaluation of JANUS shows th...

• Type: Journal
• Year: 2012
• Where: PLDI
• Authors: Omer Tripp, Roman Manevich, John Field, Mooly Sagiv
• Keywords: Concurrent Transactions, Order Of Magnitude, PLDI 2012, Programming Languages, World Benchmarks