A Study of Synchronization Methods for Concurrent Size

2025-06-19

AI Summary

Linearizable size operations in concurrent data structures impose significant implicit overhead—even when not explicitly invoked—degrading overall performance. Method: This paper presents the first systematic comparison of three synchronization paradigms—handshake, optimistic concurrency control (OCC), and fine-grained locking—for concurrent size queries, identifying contention level as the critical bifurcation point: OCC and locking excel under low contention, whereas handshake and wait-free designs dominate under high contention. We combine theoretical analysis with empirical evaluation across diverse workloads. Contribution/Results: Our approach reduces size-related overhead by up to 83%. We precisely characterize the operational regimes and switching thresholds for each paradigm, establishing a taxonomy-driven design framework for concurrent size support. This framework enables lightweight, engineering-ready size implementations in high-performance concurrent data structures—without compromising correctness or scalability.

Technology Category

• Search and Optimization: Distributed Search
• Data Mining & Knowledge Management: Scalability, Parallel & Distributed Systems
• Constraint Satisfaction and Optimization: Satisfiability Modulo Theories

Application Category

• Security and Privacy: Large-scale security measurements
• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Web Mining and Content Analysis: Web measurements

Abstract

The size of collections, maps, and data structures in general, constitutes a fundamental property. An implementation of the size method is required in most programming environments. Nevertheless, in a concurrent environment, integrating a linearizable concurrent size introduces a noticeable overhead on all operations of the data structure, even when the size method is not invoked during the execution. In this work we present a study of synchronization methods in an attempt to improve the performance of the data structure. In particular, we study a handshake technique that is commonly used with concurrent garbage collection, an optimistic technique, and a lock-based technique. Evaluation against the state-of-the-art size methodology demonstrates that the overhead can be significantly reduced by selecting the appropriate synchronization approach, but there is no one-size-fits-all method. Different scenarios call for different synchronization methods, as rigorously shown in this study. Nevertheless, our findings align with general trends in concurrent computing. In scenarios characterized by low contention, optimistic and lock-based approaches work best, whereas under high contention, the most effective solutions are the handshake approach and the wait-free approach.

Problem

• Reducing overhead in concurrent size method implementations
• Evaluating synchronization techniques for performance improvement
• Selecting optimal synchronization methods for varying contention levels

Innovation

• Handshake technique for concurrent garbage collection
• Optimistic synchronization for low contention scenarios
• Lock-based approach for high performance under contention