Disentangling multi-object operations

Abstract

We consider the problem of implementing atomic operations on multiple shared memory objects, in systems which directly support only single-object atomic operations. Our motivation is to design algorithms that exhibit both low contention between concurrent operations and a high level of concurrency, by disentangling long chains of conflicting operations. That is, operations that access widely disjoint parts of a data structure, or are widely separated in time, should not interfere with each other. The algorithm reported here extends and is based on the work of Attiya and Dagan [AD96], where a non-blocking solution is presented for two-object atomic operations. For any number, k, we present a wait-free solution for atomically accessing up to k objects. Notions of local contention and local step complexity are defined, and it is shown that the solution has low local contention and local step complexity. Relations between multi-objects and the familiar resource allocation problem are explored-the algorithm presented also provides a solution to the resource allocation problem.