SI2-SSI: Collaborative Proposal: Performance Application Programming Interface for Extreme-Scale Environments (PAPI-EX)

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Modern High Performance Computing (HPC) systems continue to increase in size and complexity. Tools to measure application performance in these increasingly complex environments must also increase the richness of their measurements to provide insights into the increasingly intricate ways in which software and hardware interact. The PAPI performance-monitoring library has provided a clear, portable interface to the hardware performance counters available on all modern CPUs and some other components of interest (scattered across the chip and system). Widely deployed and widely used, PAPI has established itself as fundamental software infrastructure, not only for the scientific computing community, but for many industry users of HPC as well. But the radical changes in processor and system design that have occurred over the past several years pose new challenges to PAPI and the HPC software infrastructure as a whole. The PAPI-EX project integrates critical PAPI enhancements that flow from both governmental and industry research investments, focusing on processor and system design changes that are expected to be present in every extreme scale platform on the path to exascale computing.The primary impact of PAPI-EX is a direct function of the importance of the PAPI library. PAPI has been in predominant use by tool developers, major national HPC centers, system vendors, and application developers for over 15 years. PAPI-EX builds on that foundation. As important research infrastructure, the PAPI-EX project allows PAPI to continue to play its essential role in the face of the revolutionary changes in the design and scale of new systems. In terms of enhancing discovery and education, the list of partners working with PAPI-EX includes NSF computing centers, major tool developers, major system vendors, and individual community leaders, and this diverse group will help facilitate training sessions, targeted workshops, and mini-symposia at national and international meetings. Finally, the active promotion of PAPI by many major system vendors means that PAPI, and therefore PAPI-EX, will continue to deliver major benefits for government and industry in many domains.PAPI-EX addresses a hardware environment in which the cores of current and future multicore CPUs share various performance-critical resources (a.k.a., 'inter-core' resources), including power management, on-chip networks, the memory hierarchy, and memory controllers between cores. Failure to manage contention for these 'inter-core' resources has already become a major drag on overall application performance. Consequently, the lack of ability to reveal the actual behavior of these resources at a low level, has become very problematic for the users of the many performance tools (e.g., TAU, HPCToolkit, Open|SpeedShop, Vampir, Scalasca, CrayPat, Active Harmony, etc.). PAPI-EX enhances and extends PAPI to solve this critical problem and prepare it to play its well-established role in HPC performance optimization. Accordingly, PAPI-EX targets the following objectives: (1) Develop shared hardware counter support that includes system-wide and inter-core measurements; (2) Provide support for data-flow based runtime systems; (3) Create a sampling interface to record streams of performance data with relevant context; (4) Combine an easy-to-use tool for text-based application performance analysis with updates to PAPI?s high-level API to create a basic, ?out of the box? instrumentation API.