Reducing Memory-Bus Energy Consumption of GPUs via Software-Based Bit-Flip Minimization

Energy consumption is a major concern in high-performance computing. One important contributing factor is the number of times the wires are charged and discharged, i.e., how often they switch from ‘0’ to ‘1’ and vice versa. We describe a software technique to minimize this switching activity in GPUs, thereby lowering the energy usage. Our technique targets the memory bus, which comprises many high-capacitance wires that are frequently used. Our approach is to strategically change data values in the source code such that loading and storing them yields fewer bit flips. The new values are guaranteed to produce the same control flow and program output. Measurements on GPUs from two generations show that our technique allows programmers to save up to 9.3% of the whole-GPU energy consumption and 1.2% on average across eight graph-analytics CUDA codes without impacting performance.