Performance Modeling, Benchmarking and Simulation of High Performance Computer Systems

11:30 - 12:00
Performance Analysis of Runtime Handling of Zero-Copy for OpenMP Programs on MI300A APUs

Carlo Bertolli, Thorsten Blass, Jan-Patrick Lehr, Doru Bercea, Dhruva Chakrabarti, Lynd Stringer, Nicole Aschenbrenner, Lawrence Meadows, Ron Liberman
AMD, USA

In current discrete GPU systems, the penalty of data movement between host and device memory is inevitable, forcing many large-scale applications to include optimizations that amortize this cost. On systems like the AMD Instinct™ MI300A series accelerators, based on the accelerated processing unit (APU) architecture, host and device memories are unified into a single physical storage. On an APU, the GPU can access memory in the same way the CPU does, thus avoiding the need for additional data movement (zero-copy). To inform developers of MI300A’s expected advantages and potential overheads, we follow an experimental approach to study our OpenMP implementation that leverages MI300A zero-copy. Performance results show that zero-copy is faster than the legacy “copy” implementation by a ratio of 1.2X-2.3X for a production-ready application, but that it incurs up to 11% penalty for one SPECaccel 2023 benchmark.