To check what a long-rerunning process is doing on linux, use
brew install strace sudo strace -p <PID> # Ctrl+C to stop dump. sudo strace -c -p <PID> # Ctrl+C to stop to get summary of count of syscalls. sudo strace -k -p <PID> # Add stack traces to each syscall to give a better idea of where in the code the syscalls are being made from.
On a Mac, use
sudo dtruss -p <PID> sudo dtruss -c -p <PID> sudo dtruss -s -p <PID> sudo dtruss df -h # Run and examine the `df -h` command.