Extending the OpenSHMEM Memory Model to Support User-Defined Spaces

OpenSHMEM is an open standard for SHMEM libraries. With the standardisation process complete, the community is looking towards extending the API for increasing programmer flexibility and extreme scalability. According to the current OpenSHMEM specification (revision 1.1), allocation of symmetric memory is collective across all PEs executing the application. For better work sharing and memory utilisation, we are proposing the concepts of teams and spaces for OpenSHMEM that together allow allocation of memory only across user-specified teams. Through our implementation we show that by using teams we can confine memory allocation and usage to only the PEs that actually communicate via symmetric memory. We provide our preliminary results that demonstrate creating spaces for teams allows for less consumption of memory resources than the current alternative. We also examine the impact of our extensions on Scalable Synthetic Compact Applications #3 (SSCA3), which is a sensor processing and knowledge formation kernel involving file I/O, and show that up to 30% of symmetric memory allocation can be eliminated without affecting the correctness of the benchmark.