Latency Impact on Spin-Lock Algorithms for Modern Shared Memory Multiprocessors

Jan Christian Meyer, Anne C. Elster


In 2006, John Mellor-Crummey and Michael Scott received the
Dijkstra Prize in Distributed Computing. This prize was for their 1991 paper
on algorithms for scalable synchronization on shared memory
multiprocessors, which included a novel spin-lock algorithm
(a.k.a. MCS spin-lock). Their spin-lock algorithm distributes spin locations
in memory to lessen the impact of bandwidth limitations. Their
empirical work and architectural suggestions
have since had a major impact on how the field has viewed spin-locks.
Motivated by emerging architectures with an increasing number of
cores, we present an empirical study on recent shared memory architectures,
including IBM P5+ and SGI ccNUMA systems. Our results show that latency
will have a much greater impact on performance than bandwidth on these and
future architectures.
Several testcases and a tabular overview of our results are included.


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