Transactional Composition of Nonblocking Data Structures

TL;DR

This paper presents NBTC, a new method for atomic composition of nonblocking data structures, enabling high concurrency and efficiency, with a practical implementation called Medley that outperforms previous systems.

Contribution

Introduces NBTC, a novel approach leveraging linearizability for atomic composition, and provides Medley, an obstruction-free implementation that enhances performance and ease of transforming data structures.

Findings

Medley outperforms LFTT by 40-170%.

Transactional overhead is approximately 2.2 times that of separate operations.

Persistent transactions achieve high throughput with epoch-based persistence.

Abstract

This paper introduces nonblocking transaction composition (NBTC), a new methodology for atomic composition of nonblocking operations on concurrent data structures. Unlike previous software transactional memory (STM) approaches, NBTC leverages the linearizability of existing nonblocking structures, reducing the number of memory accesses that must be executed together, atomically, to only one per operation in most cases (these are typically the linearizing instructions of the constituent operations). Our obstruction-free implementation of NBTC, which we call Medley, makes it easy to transform most nonblocking data structures into transactional counterparts while preserving their liveness and high concurrency. In our experiments, Medley outperforms Lock-Free Transactional Transform (LFTT), the fastest prior competing methodology, by 40--170%. The marginal overhead of Medley's transactional composition, relative to separate operations performed in succession, is roughly 2.2$\times$. For persistent data structures, we observe that failure atomicity for transactions can be achieved "almost for free" with epoch-based periodic persistence. Toward that end, we integrate Medley with nbMontage, a general system for periodically persistent data structures. The resulting txMontage provides ACID transactions and achieves throughput up to two orders of magnitude higher than that of the OneFile persistent STM system.