Abstract-Dynamic Voltage Frequency Scaling (DVFS) has been the tool of choice for balancing power and performance in high-performance computing (HPC). With the introduction of Intel's Sandy Bridge family of processors, researchers now have a far more attractive option: user-specified, dynamic, hardware-enforced processor power bounds. In this paper we provide a first look at this technology in the HPC environment and detail both the opportunities and potential pitfalls of using this technique to control processor power.As part of this evaluation we measure power and performance for single-processor instances of several of the NAS Parallel Benchmarks. Additionally, we focus on the behavior of a single benchmark, MG, under several different power bounds. We quantify the well-known manufacturing variation in processor power efficiency and show that, in the absence of a power bound, this variation has no correlation to performance. We then show that execution under a power bound translates this variation in efficiency into variation in performance.
We present a scalable temporal order analysis technique that supports debugging of large scale applications by classifying MPI tasks based on their logical program execution order. Our approach combines static analysis techniques with dynamic analysis to determine this temporal order scalably. It uses scalable stack trace analysis techniques to guide selection of critical program execution points in anomalous application runs. Our novel temporal ordering engine then leverages this information along with the application's static control structure to apply data flow analysis techniques to determine key application data such as loop control variables. We then use lightweight techniques to gather the dynamic data that determines the temporal order of the MPI tasks. Our evaluation, which extends the Stack Trace Analysis Tool (STAT), demonstrates that this temporal order analysis technique can isolate bugs in benchmark codes with injected faults as well as a real world hang case with AMG2006.
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