Models for Performance Prediction of Cache Coherence Protocols
msra(2007)
摘要
In a modern shared memory multiprocessor, it is possible to support more than one protocol for maintaining cache coherence. Possible candidates might be based on the Write-Back/Invalidate, Write-Through/Invalidate, and Write-Update protocols. Hybrid protocols allow the use of different protocols for different data blocks, and dynamic hybrid protocols additionally allow for changes in the choice of protocol during the execution of an application. In this paper, we introduce a set of analytical models for predicting the performance of parallel applications under various cache coherence protocol assumptions. These models can be used at com- pile time to determine which protocols are to be used for which data blocks, and also to determine when to change protocols in the case of dynamic protocols. Although we focus on tightly-coupled multiprocessor systems, the models apply equally well to loosely-coupled distributed systems such as networks of workstations. Our models are unique in that they lie between a large body of theoretical models that assume independence and a uniform distribution of memory accesses across processors, and a large body of address-trace oriented models that assume the availability of a precise characterization of interleaving behavior of memory accesses. The former are not very realistic, and the latter are not suitable for compile-time and run-time usage. In contrast, our models use a set of parameters that characterize the access behavior of applications well, and can be obtained with advanced compiler technology. We present the models and show how the required parameters can be obtained. We assess the accuracy of our models on 15 parallel applications and show that we can predict performance within a 10% margin. As part of this study, we also show the potential advantage of using dynamic hybrid protocols.
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关键词
cache coherence,memory access behavior,distributed shared memory,analytical performance pre- diction,dynamic hybrid protocols.,performance evaluation
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