Memory usage in module attributes

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1

This is a question I asked on the elixir-lang-core list and it should have been posted here:

Silly Erlang/Elixir beam question.

If I have a module like so:

defmodule Foo do
  @data %{:foo => "foo", :bar => "bar"}

  def getData(), do: @data
end

spawn fn() ->
  x = Foo.getData()
  # Do something with x
  :timer.sleep(100000)
end

spawn fn()->
  x = Foo.getData()
  # Do something with x
  :timer.sleep(100000)
end

How many copies of

%{:foo => "foo", :bar => "bar"}

are there in memory? Does each process make a copy of the data in it’s stack or do both process point to the same copy in some code space, etc.

Thanks!

-Chris

From Jose:

literals in your code, such as module attributes, are stored in the literal pool. So it is only one copy until you modify it.

From Michał:

Additionally the literal pool is excluded from regular garbage collection (since it never changes), so that’s an additional efficiency gain

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