Why is &__MODULE__.local/n faster than &local/n?

[sabiwara]

You might want to check these similar threads about this topic:

Anonymous function in Elixir - best to use function captures?

Been reading telementry source code when I stumbled upon this comment block. Does anyone have any references or articles about this? %% <b>Note:</b> due to how anonymous functions are implemented in the Erlang VM, it is best to use %% function captures (i.e. `fun mod:fun/4' in Erlang or `&Mod.fun/4' in Elixir) as event handlers %% to achieve maximum performance. In other words, avoid using literal anonymous functions %% (`fun(...) -> ... end' or `fn ... -> ... end') or local function captures (…

Is &foo/1 really faster than &foo(&1)

There’s however a difference between &Module.fun/2 vs. any other form. The fully quantified version (mod, fun and arity) can be optimized to not use an anonymous function, which makes it more performant. This is important in situations like :telementry handlers, which might be called very often, as described in the docs: https://hexdocs.pm/telemetry/1.1.0/telemetry.html#attach/4

There is a proposal discussing this as well:
https://groups.google.com/g/elixir-lang-core/c/rW_BRCULsGk/m/9rrYEwwtAwAJ