Scalable and Lock-Free Concurrent Dictionaries

Paper in proceeding, 2004

We present an efficient and practical lock-free implementation of a concurrent dictionary that is suitable for both fully concurrent (large multi-processor) systems as well as pre-emptive (multi-process) systems. Many algorithms for concurrent dictionaries are based on mutual exclusion. However, mutual exclusion causes blocking which has several drawbacks and degrades the system's overall performance. Non-blocking algorithms avoid blocking, and are either lock-free or wait-free. Our algorithm is based on the randomized sequential list structure called Skiplist, and implements the full set of operations on a dictionary that is suitable for practical settings. In our performance evaluation we compare our algorithm with the most efficient non-blocking implementation of dictionaries known. The experimental results clearly show that our algorithm outperforms the other lock-free algorithm for dictionaries with realistic sizes, both on fully concurrent as well as pre-emptive systems.