There are a few things you can do. Observer (and observer_cli) allow you to inspect what processes are currently doing. In observer_cli, if you ordered the processes by memory usage and you want to inspect the first one, simply press 1. You can then, for example, inspect the messages of the process or its state.
The same you can do also from iex. To get the state of a process use sys.get_state(pid). And via Process.info(pid) (or better Recon.info(pid) which disables some of the unsafe inspections) you can look into, for example, current stacktrace, process dictionary, messages etc.
