Accurate performance estimation of future many-node machines is challenging because it requires detailed simulation models of both node and network. However, simulating the full system in detail is unfeasible in terms of compute and memory resources. State-of-the-art techniques use a two-phase approach that combines detailed simulation of a single node with network-only simulation of the full system. We show that these techniques, where the detailed node simulation is done in isolation, are inaccurate because they ignore two important node-level effects: compute time variability, and inter-node communication. We propose a novel three-stage simulation method to allow scalable and accurate many-node simulation, combining native profiling, detailed node simulation and high-level network simulation. By including timing variability and the impact of external nodes, our method leads to more accurate estimates. We validate our technique against measurements on a multi-node cluster, and report an average 6.7% error on 64 nodes (maximum error of 12%), compared to on average 27% error and up to 54% when timing variability and the scaling overhead are ignored. At higher node counts, the prediction error of ignoring variable timings and scaling overhead continues to increase compared to our technique, and may lead to selecting the wrong optimal cluster configuration. Using our technique, we are able to accurately project performance to thousands of nodes within a day of simulation time, using only a single or a few simulation hosts. Our method can be used to quickly explore large many-node design spaces, including node micro-architecture, node count and network configuration.

翻译：对未来的多节点机器进行精确的性能评估极具挑战性，因为需要同时详细模拟节点和网络。然而，全系统精细模拟在计算和内存资源上并不可行。现有技术采用两阶段方法，将单节点的详细模拟与全系统的网络模拟相结合。研究表明，这些孤立进行详细节点模拟的技术忽略了两个重要的节点级效应：计算时间变化和节点间通信，因此不够精确。我们提出了一种新颖的三阶段模拟方法，结合原生性能分析、详细节点模拟和高级网络模拟，实现可扩展且精确的多节点模拟。通过包含时间变化性和外部节点的影响，我们的方法能够得出更精确的估计。我们在多节点集群上通过实测验证了该技术，报告64个节点上的平均误差为6.7%（最大误差12%），相比之下，忽略时间变化性和扩展开销时平均误差为27%，最高达54%。在更高节点数下，与我们的技术相比，忽略可变时序和扩展开销的预测误差持续增大，可能导致选择错误的最优集群配置。利用我们的技术，仅需单个或少数模拟主机，即可在一天模拟时间内精确预测数千节点的性能。该方法可用于快速探索大规模多节点设计空间，包括节点微架构、节点数量和网络配置。