Issue No. 08 - August (2003 vol. 52)
Deepu Talla , IEEE
Lizy Kurian John , IEEE
Doug Burger , IEEE
<p><b>Abstract</b>—Multimedia SIMD extensions such as MMX and AltiVec speed up media processing; however, our characterization shows that the attributes of current general-purpose processors enhanced with SIMD extensions do not match very well with the access patterns and loop structures of media programs. We find that 75 to 85 percent of the dynamic instructions in the processor instruction stream are supporting instructions necessary to feed the SIMD execution units rather than true/useful computations, resulting in the underutilization of SIMD execution units (only 1 to 12 percent of the peak SIMD execution units' throughput is achieved). Contrary to focusing on exploiting more data-level parallelism (DLP), in this paper, we focus on the instructions that support the SIMD computations and exploit both fine and coarse-grained instruction level parallelism (ILP) in the supporting instruction stream. We propose the MediaBreeze architecture that uses hardware support for efficient address generation, looping, and data reorganization (permute, packing/unpacking, transpose, etc.). Our results on multimedia kernels show that a 2-way processor with SIMD extensions enhanced with MediaBreeze provides a better performance than a 16-way processor with current SIMD extensions. In the case of application benchmarks, a 2-/4-way processor with SIMD extensions augmented with MediaBreeze outperforms a 4-/8-way processor with SIMD extensions. A first-order approximation using ASIC synthesis tools and cell-based libraries shows that this acceleration is achieved at a 10 percent increase in area required by MMX and SSE extensions (0.3 percent increase in overall chip area) and 1 percent of total processor power consumption.</p>
Media processing, subword parallelism, bottlenecks in SIMD extensions, workload characterization, performance evaluation, hardware address generation, low-overhead looping, data reorganization, superscalar general-purpose processors.
L. K. John, D. Talla and D. Burger, "Bottlenecks in Multimedia Processing with SIMD Style Extensions and Architectural Enhancements," in IEEE Transactions on Computers, vol. 52, no. , pp. 1015-1031, 2003.