Reducing the cost of power monitoring with DC wattmeters

The use of internal DC wattmeters, connected to the ATX lines that distribute power from the supply unit to the computer components, is a luring method to profile power in server configurations due to the accurate and complete information provided by this approach. In this paper we enhance the appeal of this type of power meters by addressing one of their main drawbacks, namely, their high cost per node for cluster facilities. In particular, we provide a practical demonstration that it is possible to obtain accurate information for the total instantaneous power dissipation of a platform (and, therefore, the total energy consumption) by composing the information obtained from a few ATX lines into a reduced model. Additionally, we formulate a systematic methodology to build this model, based on a small number of calibration runs involving three standard benchmarks, that allows i) to detect the minimum number of lines to profile; ii) to identify/select the most appropriate lines; and iii) to assign weights in order to build the reduced model. Our hypothesis is contrasted and experimentally validated using the complete collection of multithreaded codes in PARSEC, on two low-cost servers equipped with Intel© and AMD© multicore technology.