Pot: Deterministic transactional execution

TL;DR

Pot is a system that achieves deterministic multithreaded execution of transactional memory programs by using preordered transactions and a new concurrency control protocol, reducing nondeterminism and overhead.

Contribution

It introduces preordered transactions and a novel protocol to enable deterministic execution with both STM and HTM, including the first use of off-the-shelf HTM for this purpose.

Findings

Deterministic execution with low overhead

Pot outperforms existing approaches

First to use off-the-shelf HTM for deterministic TM

Abstract

This paper presents Pot, a system that leverages the concept of preordered transactions to achieve deterministic multithreaded execution of programs that use Transactional Memory. Preordered transactions eliminate the root cause of nondeterminism in transactional execution: they provide the illusion of executing in a deterministic serial order, unlike traditional transactions which appear to execute in a nondeterministic order that can change from execution to execution. Pot uses a new concurrency control protocol that exploits the serialization order to distinguish between fast and speculative transaction execution modes in order to mitigate the overhead of imposing a deterministic order. We build two Pot prototypes: one using STM and another using off-the-shelf HTM. To the best of our knowledge, Pot enables deterministic execution of programs using off-the-shelf HTM for the first time. An experimental evaluation shows that Pot achieves deterministic execution of TM programs with low overhead, sometimes even outperforming nondeterministic executions, and clearly outperforming the state of the art.