Using speculative retirement and larger instruction windows to narrow the performance gap between memory consistency models
Using speculative retirement and larger instruction windows to narrow the performance gap between memory consistency models
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使用推测性退休和更大的指令窗口来缩小内存一致性模型之间的性能差距
DOI：
10.1145/258492.258512
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
S. Adve
中科院分区：
文献类型：
--
作者：
Parthasarathy Ranganathan;Vijay S. Pai;S. Adve
本文研究了提高ILP处理器共享内存多处理器内存一致性模型性能的技术。本文的第一部分通过研究当前硬件优化对存储器一致性实现、硬件控制的非绑定预取和推测性加载执行对处理器一致性（PC）存储器模型的性能的影响，扩展了先前的工作。我们发现，在某些情况下，PC的优化实现比顺序一致性（SC）的最佳实现表现得更好，因为PC放松了SC的存储到加载顺序约束。然而，在某些情况下，发布一致性（RC）提供了显着的好处，因为PC遭受过早的存储预取和内存队列大小不足的负面影响。本文的第二部分提出并评估了一种新的技术，推测退休，以提高SC的性能。推测退休的影响，存储到加载约束SC允许负载和后续指令推测提交或退休，即使以前的存储是杰出的。推测性引退需要额外的硬件支持（以历史缓冲器的形式）来从由于这种推测性引退而导致的可能的一致性违反中恢复。通过64个元素的历史缓冲器，投机性退休将SC和PC之间的执行时间差距减少到11%以内，适用于我们基础架构上的所有应用程序; SC和RC之间仍然存在显著的差距。我们的论文的第三部分评估的各种技术与更大的指令窗口大小的相互作用。当增加指令窗口大小时，最初，由于增加的加载和存储重叠，所有模型的先前最佳实现通常在性能上有所改善。随着进一步的增加，PC和RC的性能稳定，而SC的性能往往下降（由于负面影响）。CCR-9410457、CCR-9502500和CDA-9502791，以及批准号为003604016的德克萨斯州先进技术计划。维贾伊派还得到了房利美和约翰赫兹基金会奖学金的支持。允许制作数字：所有或所有本材料的副本，无论是个人使用还是课堂使用，都是免费的，前提是IIUNW的副本不是为了盈利或商业利益而制作或分发的。wspvright通知、出版物的标题及其dak appesr和nuticx w给予tlmt版权是由ACM许可的。IIW。复制Aerviw，10重新出版。10张贴在服务器上或10重新分发10 IisLs需要<pccilic许可或费用。V 'A4 97纽波特，罗得岛Iskmd I.伊萨版权1997 ACM 0-89791 -890-8/97/06..$ 3.50以前的优化），扩大了模型之间的差距。在较低的基本指令窗口大小下，推测性引退有时会被指令窗口大小的等效增加所超越（因为后者也提供了加载重叠）。然而，在RC稳定的点之外，推测性引退提供了与等效指令窗口增加相当或更好的益处，并且可能具有更低的复杂性。
This paper studies techniques to improue the performance of memory consistency models for shared-memory multiprocessors with ILP processors. The first part of this paper extends earlier work by studying the impact of current hardware optimization to memory consistency implementations, hardware-controlled non-binding prefetching and speculative load execution, on the performance of the processor consistency (PC) memory model. We find that the optimized implementation of PC performs significant tly better than the best implementation of sequential consistency (SC) in some cases because PC relaxes the store-to-load ordering constraint of SC. Nevertheless, release consistency (RC) provides significant benefits over PC in some cases, because PC’ suffers from the negative ef7ects of premature store prefetches and insufficient memory queue sizes. The second part of the paper proposes and evaluates a new technique, speculative retirement, to improve the performance of SC. Speculative retirement alleviates the impact of the store-to-load constraint of SC by allowing loads and subsequent instructions to speculatively commit or retire, even while a previous store is outstanding. Speculative retirement needs additional hardware support (in the form of a history bu~er) to recover from possible consistency violations due to such speculative retires. With a 64 element history bufler, speculative retirement reduces the execution time gap between SC and PC to within 11% for ail our applications on our base architecture; a significant, though reduced, gap still remains between SC and RC. The third part of our paper evaluates the interactions of the various techniques with larger instruction window sizes. When increasing instruction window size, initially, the previous best implementations of all models generally improve in performance due to increased load and store overlap. With further increases, the performance of PC and RC stabilizes while that of SC often degrades (due to negative eflects of “This work is supported in part by the National Science Foundation under Grant NcJ. CCR-9410457, CCR-9502500, and CDA-9502791, and the Texas Advanced Technology Program under Grant No. 003604016. Vijay S. Pai is also supported by a Fannie and John Hertz Foundation Fellowship. Permission to make digit: d/lmrdcopies of all or IMUIot’this nmteria I Iiir personal or classroom use is granted without fee provided IIUNW copies are not made or distributed I’orprofit or commercial advantage. the wspvright notice, the title of the publication and its dak appesr, and nuticx w given tlmt copyright is by permission of the ACM. IIW.TO copy Aerwiw, 10 republish. 10 post on servers or 10 redistribute 10 IisLs requires <pccilic permission antior fee .V’A4 97 Newport, Rhode Iskmd I.ISA Copyright 1997 ACM 0-89791 -890-8/97/06 ..$3.50 previous optimizations), widening the gap between the models. At low base instruction window sizes, speculative retirement is sometimes outperformed by an equivalent increase in instruction window size (becausethe latter also provides load overlap). However, beyond the point where RC stabilizes, speculative retirement gives comparable or better benefit than an equivalent instruction window increase, with possibly less complexity.