Proposition of Criteria for Aborting Transaction Based on Log Data Size in LogTM

Lock-based synchronization techniques are commonly used in parallel programming on multi-core processors. However, lock can cause deadlocks and poor scalabilities. Hence, LogTM has been proposed and studied for lock-free synchronization. LogTM is a kind of hardware transactional memory. In LogTM, transactions are executed speculatively to ensure serializability and atomicity. LogTM stores original values in a log before it is modified by a transaction. If a transaction accesses a shared datum which has been accessed by another transaction running in parallel, LogTM detects it as conflict and restores all data from the associated log and restarts the transaction. This is called aborting. On abort, the costs for restoring data from a log increases in proportion to the data size on the log. However, LogTM selects which transaction should be aborted by their initiated time. Hence, if conflicts occur frequently, it may degrades the performance. This paper proposes a criterion for selecting which transaction should be aborted taking account of data size in each log. In addition, another criterion which takes account of degree of conflict is also proposed. The result of the experiment with SPLASH-2 benchmark suite programs shows that the proposed methods improve the performance 2.7% in maximum.