Diffing subject and comparison traces. The subject and comparison traces can be matched based on identifying similar work being performed by their represented entities. The diffing includes identifying first function calls from the subject trace and identifying second function calls the comparison trace. First and second call trees are created from these function calls; parent-to-child node relationships in the call trees represent caller-to-callee function relationships. A differencing tree is created from the call trees; differencing tree nodes indicate a differencing status between the first and second call trees, and a differencing cost based on the nodes' differencing status pus an aggregation of the node's descendants' differencing costs. A differencing tree node is identified based on following nodes that most contribute to differences between the first and second call trees, and it is used to provide an indicia of a difference between the first and second function calls.