Comparisons of core and uncore frequency scaling modes in quantum chemistry application GAMESS

Abstract

Energy efficiency and energy-proportional computing have become a central focus in modern supercomputers. With the exascale computing throughput purported to be bound by the 20 MW power wall, there is an urgent need for power efficiency in modern computing systems. Apart from processor cores and DRAM, the other chip components (typically collectively denoted as uncore) become increasingly important contributors to the total system power. In this paper, the uncore frequency scaling (UFS) is explored with respect to its effect on latencies and bandwidths. Next, UFS and core dynamic voltage and frequency scaling (DVFS) are compared as to their energy-saving potential through experiments on a 20-core Haswell-EP machine using the quantum chemistry application GAMESS. Results depict that UFS is comparable to DVFS in terms of power saving capability and when used in conjunction with DVFS, it can save energy up to 21% for GAMESS execution.