PowerProbe: Run-time Power Modeling Through Automatic RTL Instrumentation

Online power monitoring represents a de-facto solution to enable energy- and power-aware run-time optimizations for current and future computing architectures. Traditionally, the performance counters of the target architecture are used to feed a software-based, power model that is continuously updated to deliver the required run-time power estimates. The solution introduces a non-negligible performance and energy overhead. Moreover, it is limited to the availability of such performance counters that, however, are not primarily intended for online power monitoring. This paper introduces PowerProbe, a run-time power monitoring methodology that automatically extracts and implements a power model from the RTL description of the target architecture. The solution does not leverage any performance counter to ensure wide applicability. Moreover, the use of ad-hoc hardware that continuously updates the power estimate minimizes both the performance and the power overheads. We employ a fully compliant OpenRisc 1000 implementation to validate PowerProbe. The results highlight an average prediction error within 9% (standard deviation less than 2%), with a power and area overheads limited to 6.89% and 4.71%,