Lock-Free Multiway Search Trees

Abstract

We propose a lock-free multiway search tree algorithm for concurrent applications with large working set sizes. Our algorithm is a variation of the randomized skip tree. We relax the ordering constraints among the nodes in the original skip tree definition. Optimal paths through the tree are temporarily violated by mutation operations, and eventually restored using online node compaction. Experimental evidence shows that our lock-free skip tree outperforms a highly tuned concurrent skip list under workloads of various proportions of operations and working set sizes. The max throughput of our algorithm is on average 41% higher than the throughput of the skip list, and 129% higher on the workload of the largest working set size and read-dominated operations.