Identification of an Entire Workload's CPU-Vmin from the n-First Seconds of its Execution Based on Performance Counters

CPU pessimistic voltage margins set by hardware designers to address voltage-noise, aging and static variations, limit the power efficiency of computing systems. These margins are necessary to avoid voltage emergencies that lead to silent data corruption and application/system crashes which are not acceptable in most situations. However, the voltage margins required by different applications may vary and, therefore, an opportunity may exist to improve the power-efficiency if we can adapt the CPU voltage margins per workload. This paper presents a comprehensive correlation analysis of an application's minimum operating voltage (CPU-Vmin) with hardware's performance counters on a real multicore system. The analysis reveals that a subset of the performance counters-the same ones across different workloads-have a strong correlation with a workload's CPU-Vmin. Moreover, the results show that the CPU-Vmin is accurately identifiable by monitoring a workload's performance-counters during the n-first seconds of its execution. Our findings serve as the basis of a software-based CPU-Vmin identification method that monitors an application for the first n-seconds and then sets the CPU supply voltage to a specific value for the rest of the execution. Our evaluation shows that when n-first equals to 20 seconds, the CPU-Vmin workload identification method provides a safe CPU-Vmin, 99.4% of the time and reduces power on average by 3.8% and 7.1% as compared to when operating at a safe and a nominal supply voltage, respectively.