Scalability versus semantics of concurrent FIFO queues

Maintaining data structure semantics of concurrent queues such as first-in first-out (FIFO) ordering requires expensive synchronization mechanisms which limit scalability. However, deviating from the original semantics of a given data structure may allow for a higher degree of scalability and yet be tolerated by many concurrent applications. We introduce the notion of a k-FIFO queue which may be out of FIFO order up to a constant k (called semantical deviation). Implementations of k-FIFO queues may be distributed and therefore be accessed unsynchronized while still being starvationfree. We show that k-FIFO queues whose implementations are based on state-of-the-art FIFO queues, which typically do not scale under high contention, provide scalability. Moreover, probabilistic versions of k-FIFO queues improve scalability further but only bound semantical deviation with high probability. Categories and Subject Descriptors

• Type: Journal
• Year: 2011
• Where: PODC
• Authors: Hannes Payer, Harald Röck, Christoph M. Kirsch, Ana Sokolova
• Keywords: Distributed And Parallel Computing, FIFO Queue, Fifo Queues, PODC 2011, Structure Semantics