Case study: Effectiveness of dynamic frequency scaling on server workload

Dynamic frequency scaling (DFS) is a feature commonly found in modern processors. It lowers the clock frequency of a core according to the load level and reduces the power consumption. In this paper, we present a case study of its effectiveness on a server platform with an AMD Phenom II x6 using the SPECjEnterprise2010 as the workload. We show that (1) DFS lowers the power consumption at low load levels significantly, but it overreacts to incidental short serge of core utilization (2) stretching the sampling period of the core utilization further reduces the power consumption, but it slows down the core to adjust its clock frequency when the load level is actually increasing, and (3) increasing the threshold level to switch the core frequency is effective when combined with a longer sampling period in the medium load level, but not in the low load levels.