TLF: Transactional Lock Fusion

Software Transactional Memory (STM) systems have made many advances over the past decades, and data structures that use STM are approaching the efficiency of hand-designed concurrent data structures. Hand-designed structures, however, still maintain a key advantage over implementations with STMs: with careful design, they can ignore "unimportant" read-write conflicts. Some of the most efficient concurrent structures, for example, are based on optimistic locking (OL). Operations that use OL have a traversal phase with no locks, where read-write conflicts are ignored, and a commit phase where conflicts are protected with fine grained locks. An STM, on the other hand, does not know which conflicts are important and will serialize all reads and writes, potentially at a significant cost.