CSR: Small: On Modeling Software Dynamics for Feedback Computing

本项目开发确保数据中心中使用的资源管理机制等大规模软件系统的性能稳定性的科学技术。术语“稳定性”在这里是在控制理论的意义上使用的，它适用于动态系统，大致意味着在一系列期望的系统状态下不发散。性能稳定性是指性能参数的稳定性，例如延迟、响应时间、服务吞吐量、利用率、缓存命中率或超时率。该项目开发了必要的基础和工具，以确保软件的稳定性，并诊断和撤销不稳定行为的根本原因，当它发生在部署的系统。一个重要的贡献在于探索规则和指导方针，如果遵守，允许推理软件的稳定性组合的方式，这样的稳定性组合系统可以推断出组件的稳定性。软件性能的组成稳定性分析是由控制理论的进步，如被动理论和积极和耗散系统的理论。这些进展提供了丰富的结果，适合软件模型的非线性系统的限制类别的稳定性和组合性。在软件设计中，性能稳定性的挑战在很大程度上被忽视了。它们通常不会出现在小型系统中，而是随着系统的规模和复杂性而增长。越来越多的软件整合和计算服务外包的趋势需要更复杂，更多的分层，以及各种资源管理机制之间的更多互动，使得更难以预测副作用，更有可能出现稳定性问题。该项目提高了当前对利用反馈机制实现性能和鲁棒性目标的大型系统的设计，执行和管理的理解。教育活动包括将项目要素纳入PI教授的几门课程，并让本科生参与研究。外展活动包括在校园内举办“反馈计算日”，结合一个大型研究会议提供关于反馈计算的教程，以及由PI努力从代表性不足的群体中招募学生。传播活动包括将研究结果记录在PI的一本书中，以及通过工业界的合作者进行技术过渡的努力。

This project develops science and technology for ensuring performance stability of large-scale software systems, such as resource management mechanisms used in data centers. The term "stability" is used here in a control-theoretic sense that applies to dynamical systems and roughly means freedom from divergence a range of desired system states. Performance stability refers to stability of performance parameters, such as latency, response time, service throughput, utilization, cache hit ratio, or timeout rate. The project develops the foundations and tools necessary to ensure software stability, and to diagnose and undo root causes of unstable behavior when it occurs in deployed systems. A significant contribution lies in exploring rules and guidelines that, if obeyed, allow reasoning about software stability in a compositional manner, such that stability of composite systems can be inferred from stability of components. Compositional stability analysis of software performance is facilitated by advances in control theory such as Passivity Theory and the Theory of Positive and Dissipative Systems. These advances offer a wealth of results on stability and compositionality for a restricted category of non-linear systems that fits software models. Performance stability challenges have been largely overlooked in software design. They are not typically manifest in small systems, but grow with the size and complexity of systems. The trend towards more software consolidation and outsourcing of computing services entails more complexity, more layering, and more interactions among various resource management mechanisms, making it harder to anticipate side-effects, and more likely there will be stability problems. The project improves the current understanding of the design, execution, and management of large systems that exploit feedback mechanisms to achieve performance and robustness objectives. Educational activities include incorporation of project elements into several courses taught by the PI, and involvement of undergraduate students in the research. Outreach activities include an on-campus "Feedback Computing Day", a tutorial on feedback computing to be offered in conjunction with a major research conference, and efforts by the PI to recruit students from under-represented groups. Dissemination activities include documentation of results of the research in a book by the PI, and efforts to transition technology through collaborators in industry.