COZ: Finding Code that Counts with Causal ProfilingCharlie Curtsinger ∗Department of Computer ScienceGrinnell Collegecurtsinger@cs.grinnell.eduEmery D. BergerCollege of Information and Computer SciencesUniversity of Massachusetts Amherstemery@cs.umass.eduAbstract Improving performance is a central concern for softwaredevelopers. To locate optimization opportunities, developersrely on software profilers. However, these profilers only reportwhere programs spent their time: optimizing that code may