Godu uses goroutines for concurrency and threads for parallelization. Each subdirectory in the directory tree is proccessed concurently with it's own goroutine and by default godu will create as many threads as logical CPUs in your system. The threads will process the pool of concurent goroutines until done. With a large directory tree with many directories, there could be many thousands of lightweight goroutines running concurently.
Usage: ./godu [-v, -t int] topdir1 topdirN
Example: ./godu -v /home/rmcdermo /fh/fast/mcdermott_r /fh/secure/research/mcdermott_r
-t int
Optional: set number of threads, defaults to number of logical cores (default 56)
-v Optional: show verbose progress messages