Raja R. Sambasivan, Alice X. Zheng, Elie Krevat, Spencer Whitman, Michael Stroucken, William Wang, Lianghong Xu, Gregory R. Ganger
Carnegie Mellon University Parallel Data Lab Technical Report CMU-PDL-10-107
Publication year: 2010

Note: This techreport has been superseded by our NSDI’11 paper, “Diagnosing performance changes by comparing request flows.”

The causes of performance changes in a distributed system often elude even its developers. This paper develops a new technique for gaining insight into such changes: comparing system behaviours from two executions (e.g., of two system versions or time periods). Building on end-to-end request flow tracing within and across components, algorithms are described for identifying and ranking changes in the flow and/or timing of request processing. The implementation of these algorithms in a tool called Spectroscope is described and evaluated. Five case studies are presented of using Spectroscope to diagnose performance hanges in a distributed storage system caused by code changes and configuration modifications, demonstrating the value and efficacy of comparing system behaviours.

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