I introduced Valgrind in Chapter 11, Managing Memory, as a tool for identifying memory problems using the memcheck tool. Valgrind has other useful tools for application profiling. The two I am going to look at here are Callgrind and Helgrind. Since Valgrind works by running the code in a sandbox, it is able to check the code as it runs and report certain behaviors, which native tracers and profilers cannot do.