I hope there is not much cost! I’ve been using a lot of super to override action/2 in controllers to handle exceptions such as redirect’s when a permission exception is thrown. ^.^
But yeah, I’ve not looked at how super is implemented, hmm…
So it seems to be implemented at:
https://github.com/elixir-lang/elixir/blob/ff8dd1af7f6b53e482cd8be304093fabd36bc6dc/lib/elixir/src/elixir_overridable.erl#L16-L22
So it looks up the previous function definition and seems to call it, and just above that is where you see it defines in ets the information of what is overridable, with the store function being at the bottom.
So, it looks like the old/parent definitions are defined with a combination of the name and a counter, so always unique, and defp’d, so calls to them are always ‘local’ calls (in erlang parlance), which is fast.
So no issue, it looks like super is fast, I’d not worry about lots of them at all. 
