SHF:Small: Hardware/Software Support for Debugging of Scaling Limiters in Many-Core Execution

直到最近，让程序运行得更快的一种经济有效的方法是购买一台配备最新处理器的计算机，而不对程序本身进行任何更改。然而，近年来这种方法不再有效-而不是一个更快的处理器核心，最近的处理器依赖于越来越多的核心来提供更好的性能。为了从这些新的多核和众核处理器中受益，程序必须明确地按“规模”编写，即，在更多的内核上运行时，为扩展而重新设计是耗时且昂贵的，特别是考虑到大多数程序员不习惯（也没有受过训练）编写使用多个内核的程序。这个由NSF资助的项目将分析程序中的伸缩问题，并以足够的准确性将其报告给程序员，以帮助快速处理问题。这种方法的一个重要方面是，它还有助于教育当前的程序员和未来的程序员（例如，大学生）预测缩放问题并在未来避免它们。还计划在亚特兰大的初中和高中（少数民族学生占人口的大多数）开展更多的推广活动，教育学生及其教师了解计算机硬件和软件的关键概念。该项目的主要技术挑战是存在多种类型的缩放问题。一些缩放问题与应用程序本身有关，例如，串行段、锁争用等，有些是与硬件相关的，例如互连带宽的争用、目录中的串行化、共享高速缓存中的容量争用等。这些问题的症状通常是模糊的，这使得程序员更难以识别和纠正它们。该项目将为分析提供硬件支持，这将有助于消除某些症状的歧义并将其归因于代码的特定部分，沿着软件工具将分析和报告软件和硬件相关的缩放限制器。我们的报告将足够具体，以引导程序员直接找到应该“修复”的代码，并帮助他们理解为什么以及如何修改这些代码。

Until recently, a cost-effective way to make a program run faster was to buy a computer with a more recent processor, without making any changes to the program itself. However, in recent years this approach no longer works - instead of one ever-faster processor core, recent processors rely on increasing numbers of cores to provide better performance. To benefit from these new multi- and many-core processors, programs must be explicitly written to "scale," i.e., to keep getting faster as they run on more cores. Re-design for scaling is time-consuming and costly, especially considering that most programmers are not used to (nor trained for) writing programs that use more than one core. This NSF-funded project will analyze scaling problems in programs and report them to programmers with enough accuracy to help rapidly deal with the problems. An important aspect of this approach is that it also helps educate current programmers and future ones (e.g., college students) to anticipate scaling problems and avoid them in the future. Additional outreach activities are planned in middle and high schools in Atlanta (where minority students are the majority of the population) to educate both students and their teachers about key concepts in computer hardware and software. The main technical challenge in this project is that there are many types of scaling problems. Some scaling problems are related to the application itself, e.g., serial sections, lock contention, etc., and some are hardware-related, such as contention for interconnect bandwidth, serialization in directories, contention for capacity in shared caches, etc. The symptoms of these problems are often ambiguous, which makes them even more difficult for programmers to identify and correct. This project will provide hardware support for profiling that will help disambiguate some of the symptoms and attribute them to specific parts of the code, along with software tools that will analyze and report both software- and hardware-related scaling limiters. Our reporting will be specific enough to lead programmers directly to the code that should be "fixed" and help them understand why and how this code needs to be modified.