OpenMDSP: Extending OpenMP to Program Multi-Core DSP

摘要

Multi-core Digital Signal Processors (DSP) are widely used in wireless telecommunication, core network transcoding, industrial control, and audio/video processing etc. Comparing with general purpose multi-processors, the multi-core DSPs normally have more complex memory hierarchy, such as on-chip core-local memory and non-cache-coherent shared memory. As a result, it is very challenging to write efficient multi-core DSP applications. The current approach to program multi-core DSPs is based on proprietary vendor SDKs, which only provides low-level, non-portable primitives. While it is acceptable to write coarse-grained task level parallel code with these SDKs, it is very tedious and error prone to write fine-grained data parallel code with them. We believe it is desired to have a high-level and portable parallel programming model for multi-core DSPs. In this paper, we propose Open MDSP, an extension of Open MP designed for multi-core DSPs. The goal of Open MDSP is to fill the gap between Open MP memory model and the memory hierarchy of multi-core DSPs. We propose three class of directives in Open MDSP: (1) data placement directives allow programmers to control the placement of global variables conveniently, (2) distributed array directives divide whole array into sections and promote them into core-local memory to improve performance, and (3) stream access directives promote big array into core-local memory section by section during a parallel loop's processing. We implement the compiler and runtime system for Open MDSP on Free Scale MSC8156. Benchmarking result shows that seven out of nine benchmarks achieve a speedup of more than 5 with 6 threads.