Folding: reporting instantaneous performance metrics and source-code references

Abstract

Despite supercomputers deliver huge computational power, applications only reach a fraction of it. There are several factors limiting the application performance, and one of the most important is the single processor efficiency because it ultimately dictates the overall achieved performance. We present the folding mechanism, a process that combines measurements captured through minimal instrumentation and coarse-grain sampling ensuring low time dilation (less than 5%). The mechanism reports instantaneous performance and source-code references for optimized binaries accurately by taking advantage of the repetitiveness of many applications, especially in HPC. The mechanism enables the exploration of the application performance and guides the analyst to source-code modifications.