Using Valgrind
I introduced Valgrind in Chapter 18 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 can check the code as it runs and report certain behaviors, which native tracers and profilers cannot do.
Callgrind
Callgrind is a call graph-generating profiler that also collects information about processor cache hit rate and branch prediction. Callgrind is only useful if your bottleneck is CPU-bound. It’s not useful if heavy I/O or multiple processes are involved.
Valgrind does not require kernel configuration, but it does need debug symbols. It is available as a target package in both The Yocto Project and Buildroot (BR2_PACKAGE_VALGRIND).
You run Callgrind in Valgrind on the target like so:
# valgrind --tool=callgrind <program>
This produces a file...
