KCachegrind visualizes profiles of program runs in various ways, including a tree map and call graph visualization, and source and assembler annotation. It is designed to be fast and to provide a quick overview of very large programs, such as KDE applications. A source for profile data is Callgrind, a Valgrind plugin, which produces call graph and cache simulation events. While this can run unmodified binaries, the simulation slows down measuring. For other profile tools like OProfile, format converters are provided.