Performance evaluation of macroblock-level parallelization of h.264 decoding on a cc-numa multiprocessor architecture
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This paper presents a study of the performance scalability of a macroblock-level parallelization of the H.264 decoder for High Definition (HD) applications on a multiprocessor architecture. We have implemented this parallelization on a cache coherent Non-uniform Memory Access (cc-NUMA) shared memory multiprocessor (SMP) and compared the results with the theoretical expectations. The study includes the evaluation of three different scheduling techniques: static, dynamic and dynamic with tail-submit. A dynamic scheduling approach with a tail-submit optimization presents the best performance obtaining a maximum speedup of 9.5 with 24 processors. A detailed profiling analysis showed that thread synchronization is one of the limiting factors for achieving a better scalability. The paper includes an evaluation of the impact of using blocking synchronization APIs like POSIX threads and POSIX real-time extensions. Results showed that macroblock-level parallelism as a very fine-grain form of Thread-Level Parallelism (TLP) is highly affected by the thread synchronization overhead generated by these APIs. Other synchronization methods, possibly with hardware support, are required in order to make MB-level parallelization more scalable.