TardisTM: incremental repair for transactional memory

Transactional memory (TM) provides developers with a transaction primitive for concurrent code execution that transparently checks for concurrency conflicts. When such a conflict is detected, the system recovers by aborting and restarting the transaction. Although correct, this behavior wastes work and inhibits forward progress.

In this paper, we present TardisTM, a software TM system that supports repairing concurrency conflicts while preserving unaffected computation. Our key insight is that existing conflict detection mechanisms can be extended to perform incremental transaction repair, when augmented with additional runtime information. To do so, we design a mechanism for localizing conflicts back to transactional program points, define the semantics for optional repair handler annotations, and extend the conflict detection algorithm to ensure all repairs are completed. To evaluate our system, we characterize the benefit of repair on a set of benchmark programs; we measure up to 2.95x speedup over mutual exclusion, and 93% abort reduction over a baseline software TM system that does not support repair.