Spectral profiling: Observer-effect-free profiling by monitoring EM emanations

This paper presents Spectral Profiling, a new method for profiling program execution without instrumenting or otherwise affecting the profiled system. Spectral Profiling monitors EM emanations unintentionally produced by the profiled system, looking for spectral “spikes” produced by periodic program activity (e.g. loops). This allows Spectral Profiling to determine which parts of the program have executed at what time. By analyzing the frequency and shape of the spectral “spike”, Spectral Profiling can obtain additional information such as the per-iteration execution time of a loop. The key advantage of Spectral Profiling is that it can monitor a system as-is, without program instrumentation, system activity, etc. associated with the profiling itself, i.e. it completely eliminates the “Observer's Effect” and allows profiling of programs whose execution is performance-dependent and/or programs that run on even the simplest embedded systems that have no resources or support for profiling. We evaluate the effectiveness of Spectral Profiling by applying it to several benchmarks from MiBench suite on a real system, and also on a cycle-accurate simulator. Our results confirm that Spectral Profiling yields useful information about the runtime behavior of a program, allowing Spectral Profiling to be used for profiling in systems where profiling infrastructure is not available, or where profiling overheads may perturb the results too much (“Observer's Effect”).