Comparing scalability prediction strategies on an SMP of CMPs

Diminishing performance returns and increasing power consumption of single-threaded processors have made chip multiprocessors (CMPs) an industry imperative. Unfortunately, poor software/hardware interaction and bottlenecks in shared hardware structures can prevent scaling to many cores. In fact, adding a core may harm performance and increase power consumption. Given these observations, we compare two approaches to predicting parallel application scalability: multiple linear regression and artificial neural networks (ANNs). We throttle concurrency to levels with higher predicted power/performance efficiency. We perform experiments on a state-of-the-art, dual-processor, quad-core platform, showing that both methodologies achieve high accuracy and identify energy-efficient concurrency levels in multithreaded scientific applications. The ANN approach has advantages, but the simpler regression-based model achieves slightly higher accuracy and performance. The approaches exhibit median error of 7.5% and 5.6%, and improve performance by an average of 7.4% and 9.5%, respectively.