Lightweight Instrumentation and Analysis Using OpenSHMEM Performance Counters.

Partitioned Global Address Space (PGAS) programming models, such as OpenSHMEM, are popular methods of parallel programming; however, performance monitoring and analysis tools for these models have remained elusive. In this work, we propose a performance counter extension to the OpenSHMEM interfaces to expose internal communication state as lightweight performance data to tools. We implement our interface in the open source Sandia OpenSHMEM library and demonstrate its mapping to libfabric primitives. Next, we design a simple collector tool to record the behavior of OpenSHMEM processes at execution time. We analyze the Integer Sort (ISx) benchmark and use the resulting data to investigate several common performance issues-including communication schedule, poor overlap, and load imbalance-and visualize the impact of optimizations to correct these issues. Through this study, our tool uncovered a performance bug in this popular benchmark. Finally, by using our tool to guide the application of several pipelining optimizations, we were able to improve the ISx key exchange performance by more than 30%.