anaging Concurrent Access for Shared Memory

Passing messages through shared memory plays an important role on symmetric multiprocessors and on Clumps. The management of concurrent access to message queues is an important aspect of design for shared memory messagepassing systems. Using both microbenchmarks and applications, this paper compares the pelformanee of concurrent access algorithms for passing active messages on a Sun Enterprise 5000 sewel: The paper presents a new lock-jree algorithm that provides many of the advantages of nonblocking algorithms while avoiding the overhead of true non-blocking behaviol: The lockfree algorithm couples synchronization tightly to the data structure and demonstrates application pelformance superior to all others studied. The success of this algorithm implies that other practical problems might also bene$t from a reexamination of the nonblocking literature.