Power Phase Variation in a Commercial Server Workload

Many techniques have been developed for adaptive power management of computing systems. These techniques rely on the presence of varying power phases to detect opportunities for adaptation. However, little information is available regarding the extent of power phases in real systems. This paper illustrates available power phases ranging from 1 millisecond to 1 second using a commercial workload running on enterprise class hardware. Data is obtained using a server instrumented for power measurement at the subsystem level. The analysis shows that chipset, memory and disk subsystems have the most homogenous phase behavior with greater than 71% of samples within phases of 100 milliseconds or shorter. In contrast, CPU and I/O subsystems have much more variation with only 26% of samples within phases of 10 milliseconds or shorter