SHF: Small: Information-Flow-Based Profiling of Concurrent Applications

随着多核革命的到来，扩展到多核对性能至关重要。即使是一小部分顺序代码也会严重限制并行性带来的性能提升。临界区将执行顺序化，因此随着内核数量的增加，性能会受到越来越大的限制。将软件扩展到多个核的经典方法首先是使锁更细粒度。这通常不足以扩展到少数核心之外；进一步扩展通常需要用新的实现替换数据结构实现。现有的分析器告诉开发人员时间花在了哪里，但是开发人员很难判断选择不当的数据结构设计的影响。通常不清楚同步开销是计算的基础还是可以通过重写实现来解决。本项目开发了一种基于信息流分析并发代码的新方法。信息流分析使这种方法能够区分作为计算基础的并发瓶颈和仅仅是特定实现的工件的瓶颈。这种方法不仅可以建议在哪些地方可以优化同步，还可以通过重写代码来消除不必要的冲突，从而确定提高性能的机会。以前的工作主要集中在检测对共享数据的冲突访问上，因此错过了这个优化机会。该项目将在FlowProf工具中实现这种新方法，该工具将公开可用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the multi-core revolution, scaling to multiple cores is critical for performance. Even small fractions of sequential code seriously limit performance gains from parallelism. Critical sections sequentialize the execution and thus increasingly limit performance as the number of cores increases. The classic approach to scaling software to many cores begins with making locks more fine-grained. This is often not sufficient to scale beyond a handful of cores; scaling further often requires data structure implementations to be replaced with new implementations. Existing profilers inform developers where time is spent, but it is hard for developers to judge the impact of poorly selected data structure designs. It is often not clear whether the synchronization overhead is fundamental to the computation or can be addressed by rewriting the implementation.This project develops a new approach to profiling concurrent code based on information flow. Information flow analysis enables this approach to differentiate between concurrency bottlenecks that are fundamental to the computation and bottlenecks that are merely artifacts of the particular implementation. This approach has the potential to not only suggest where synchronization can be optimized but can also identify opportunities to improve performance by rewriting to code to eliminate superfluous conflicts. Previous work focused mostly on detecting conflicting accesses to shared data and thus missed this optimization opportunity. The project will implement this new approach in the FlowProf tool which will be publicly available.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.