Understanding , Detecting , and Repairing Performance Bugs

Software performance is critical for how end-users perceive the quality of software products. Performance bugs—programming errors that cause performance degradation—lead to poor user experience and low system throughput. Despite advances in profiling techniques, performance bugs still escape in production runs. There are two key reasons why performance bugs are not effectively detected during in-house testing. First, there is little available data about how performance bugs are discovered, reported, and fixed in practice. Such data is required when designing effective techniques for addressing performance bugs. Second, the current techniques for detecting performance bugs detect only slow computation and do not address other important parts of the testing process, such as automated oracles or bug fixing. This dissertation makes three contributions. The first contribution is a study of how performance bugs are discovered, reported to developers, and fixed by developers, and how these results compare with the results for non-performance bugs. The study considers performance and nonperformance bugs from three popular code bases: Eclipse JDT, Eclipse SWT, and Mozilla. First, we find little evidence that fixing performance bugs has a higher chance to introduce new functional bugs than fixing non-performance bugs, which implies that developers may not need to be overconcerned about fixing performance bugs. Second, although fixing performance bugs is about as error-prone as fixing non-performance bugs, fixing performance bugs is more difficult than fixing non-performance bugs, indicating that developers need better tool support for fixing performance bugs and testing performance bug patches. Third, unlike many non-performance bugs, a large percentage of performance bugs are discovered through code reasoning, not through users observing the negative effects of the bugs (e.g., performance degradation) or through profiling. The result