Caramel: Detecting and fixing performance problems that have nonintrusive fixes

Abstract—Performance bugs are programming errors that slow down program execution. While existing techniques can detect various types of performance bugs, a crucial and practical aspect of performance bugs has not received the attention it deserves: how likely are developers to fix a performance bug? In practice, fixing a performance bug can have both benefits and drawbacks, and developers fix a performance bug only when the benefits outweigh the drawbacks. Unfortunately, for many performance bugs, the benefits and drawbacks are difficult to assess accurately. This paper presents CARAMEL, a novel static technique that detects and fixes performance bugs that have non-intrusive fixes likely to be adopted by developers. Each performance bug detected by CARAMEL is associated with a loop and a condition. When the condition becomes true during the loop execution, all the remaining computation performed by the loop is wasted. Developers typically fix such performance bugs because these bugs waste computation in loops and have non-intrusive fixes: when some condition becomes true dynamically, just break out of the loop. Given a program, CARAMEL detects such bugs statically and gives developers a potential source-level fix for each bug. We evaluate CARAMEL on real-world applications, including 11 popular Java applications (e.g., Groovy, Log4J, Lucene, Struts, Tomcat, etc) and 4 widely used C/C+