An O(1) time complexity software barrier

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Publication Type technical report
School or College College of Engineering
Department Computing, School of
Program Advanced Research Projects Agency
Creator Carter, John B.
Other Author Cheng, Liqun
Title An O(1) time complexity software barrier
Date 2004
Description As network latency rapidly approaches thousands of processor cycles and multiprocessors systems become larger and larger, the primary factor in determining a barrier algorithm?s performance is the number of serialized network latencies it requires. All existing barrier algorithms require at least O(log N) round trip message latencies to perform a single barrier operation on an N-node shared memory multiprocessor. In addition, existing barrier algorithms are not well tuned in terms of how they interact with modern shared memory systems, which leads to an excessive number of message exchanges to signal barrier completion. The contributions of this paper are threefold. First, we identify and quantitatively analyze the performance deficiencies of conventional barrier implementations when they are executed on real (non-idealized) hardware. Second, we propose a queue-based barrier algorithm that has effectively O(1)time complexity as measured in round trip message latencies. Third, by exploiting a hardware write-update (PUT) mechanism for signaling, we demonstrate how carefully matching the barrier implementation to the way that modern shared memory systems operate can improve performance dramatically. The resulting optimized algorithm only costs one round trip message latency to perform a barrier operation across N processors. Using a cycle-accurate execution-driven simulator of a future-generation SGI multiprocessor, we show that the proposed queue-based barrier outperforms conventional barrier implementations based on load-linked/storeconditional instructions by a factor of 5.43 (on 4 processors) to 93.96 (on 256 processors).
Type Text
Publisher University of Utah
Subject Network latency; Barrier algorithm; Time complexity software barrier
Subject LCSH Multiprocessors
Language eng
Bibliographic Citation Cheng, Liqun; Carter, John B. (2004). An O(1) time complexity software barrier. UUCS-04-018.
Series University of Utah Computer Science Technical Report
Relation is Part of ARPANET
Rights Management ©University of Utah
Format Medium application/pdf
Format Extent 407,729 bytes
Source University of Utah School of Computing
ARK ark:/87278/s6n87v3h
Setname ir_uspace
Date Created 2012-06-13
Date Modified 2021-05-06
ID 704246
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