CSR: Small: Enabling Dual-mode Execution for Removing I/O Bottleneck: A Highly Applicable Design and Implementation

保持高并行性对于有效使用基于多核和集群的并行系统至关重要，但这可能与I/O效率不一致，导致I/O密集型并行应用程序的性能不佳。I/O堆栈不同级别的请求处理策略的效率依赖于来自不同进程的请求的局部性。 进程是I/O请求的生产者，它们的调度决定了请求发出的时间和来自不同进程的请求之间的局部性。当一个程序被I/O检查时，其进程的调度直接影响存储系统？的效率，从而该计划？的执行时间。 在这种情况下，调度策略，旨在提高请求局部性，优先于通常的目标，如负载平衡和公平性，预计将提高整体效率的I/O栈和改善I/O bottlenecks.The调查员提出了一个双模式执行，将一个新的数据驱动模式，以补充正常的语句驱动模式。 在数据驱动模式中，进程被调度为使得它们将以改进的局部性发出请求，并且将消耗已经被有效地预取的数据。这个为期12个月的项目的研究重点是调查和了解进程调度对I/O性能的积极影响程度。它考虑了I/O强度的差异、各个进程的I/O访问模式以及读写比率。研究人员将在不同的I/O层，包括I/O库，系统缓冲区和I/O调度程序，与各种假设的I/O感知进程调度策略的I/O性能行为进行广泛的检查。这项研究将揭示所提出的双模式执行的潜在优点，并描绘了支持它的算法的设计空间，它也将确定潜在的设计和实现的陷阱和限制。通过这样做，该项目有望为引入一种用于缓解I/O瓶颈的破坏性技术铺平道路。

Maintaining high parallelism is critical for efficient use of multicore- and cluster-based parallel systems, but this can be at odds with I/O efficiency, resulting in suboptimal performance of I/O-intensive parallel applications. The efficiency of request-processing policies at different levels of the I/O stack relies on the locality of requests from various processes. Processes are the producers of I/O requests, and their scheduling determines the timing of request issuance and the locality among requests from different processes. When a program is I/O bottlenecked the scheduling of its processes directly affects the storage system?s efficiency, and thus the program?s execution time. In such scenarios, a scheduling policy designed to improve request locality, in preference to the usual objectives such as load balance and fairness, is expected to improve the overall efficiency of the I/O stack and ameliorate I/O bottlenecks.The investigator proposes a dual-mode execution, incorporating a new data-driven mode to complement the normal statement-driven mode. In the data-driven mode processes are scheduled such that they will issue requests with improved locality, and will consume data that has been efficiently pre-fetched. The research focus of this 12-month project is the investigation and understanding of the extent to which process scheduling can positively affect I/O performance. It takes into account variance of I/O intensity, I/O access pattern of individual processes, and the ratio of reads and writes. The investigator will perform an extensive examination of I/O performance behaviors at different I/O layers, including the I/O library, system buffer, and I/O scheduler, with various hypothetical I/O-aware process scheduling strategies. This research will reveal the potential merits of the proposed dual-mode execution, and delineate the design space for algorithms supporting it. It will also identify pitfalls and limits of potential designs and their implementations. By so doing, this project is expected to pave the road to the introduction of a disruptive technique for mitigating I/O bottlenecks.