Practical Concurrent Unrolled Linked Lists Using Lazy Synchronization

Linked lists and other list-based sets are one of the most ubiquitous data structures in computer science. They are useful in their own right and are frequently used as building blocks in other data structures. A linked list can be “unrolled” to combine multiple keys in each node; this improves storage density and overall performance. This organization also allows an operation to skip over nodes which cannot contain a key of interest. This paper introduces a new high-performance concurrent unrolled linked list with a lazy synchronization strategy that allows wait-free read operations. Most write operations under this strategy can complete by locking a single node. Experiments show up to a 400% improvement over other concurrent list-based sets.