A Scalable Shared Queue on a Distributed Memory Machine

The emergence of low latency, high throughput routers means that network locality issues no longer dominate the performance of parallel algorithms. One of the key performance issues is now the even distribution of work across the machine, as the problem size and number of processors increase. This paper describes the implementation of a highly scalable shared queue, supporting the concurrent insertion and deletion of elements. The main characteristics of the queue are that there is no xed limit on the number of outstanding requests and the performance scales linearly with the number of processors (subject to increasing network latencies). The queue is implemented using a general purpose computational model, called the WPRAM. The model includes a shared address space which uses weak coherency semantics. The implementation makes extensive use of pairwise synchronisation and concurrent atomic operations to achieve scalable performance. The WPRAM is targeted at the class of distributed memory machines which use a scalable interconnection network.