Looking at this PR <https://github.com/beam-telemetry/telemetry/pull/43> (when the recommendation to use external functions was added to :telemetry)
... when anonymous functions are copied into the process heap from ETS, a global reference counter is incremented ... And from this comment <https://github.com/beam-telemetry/telemetry/pull/43#issuecomment-840179783> : With the global capture, the function isn't copied and therefore doesn't need to be garbage collected when invoked. On Sunday, March 24, 2024 at 6:13:14 PM UTC-7 sabi...@gmail.com wrote: > This is an interesting topic. > > I tried to benchmark these and sometimes local functions indeed show up as > slightly slower, but it is typically in the 0~2% range even for this > contrived example doing basically nothing. So I'm not sure if it is worth > highlighting the difference: > > https://github.com/sabiwara/elixir_benches/commit/9b721f3b19f8af9d9d63a30618cdafeaa6367883 > > Checking the S file shows that external functions are just literals while > local functions are calling make_fun3: > > https://github.com/sabiwara/elixir_benches/commit/9b721f3b19f8af9d9d63a30618cdafeaa6367883#diff-3a3b83d8acad1d3b6faed87ba471843f4424b22c26c179bf1d86a87a880e8223R74-R93 > > Even though, as far as I know, recent versions of Erlang > have optimizations to make sure the overhead of lambdas like this one > remains very small: https://github.com/erlang/otp/pull/6963. > > > Le dim. 24 mars 2024 à 01:50, 'Rudolf Manusadzhian' via elixir-lang-core < > elixir-l...@googlegroups.com> a écrit : > >> Hi there! Might be a naive question. >> >> Why don't we treat all local captures as external? Like at compile time, >> if it's possible, we could treat *&fun/0* as *&__MODULE__.fun/0* and get >> a free performance boost, if in the end they behave same. >> >> I was going thought the docs for :telemetry.attach/4 >> <https://hexdocs.pm/telemetry/1.2.1/telemetry.html#attach/4> and the >> suggestion to avoid using *local* captures raise that thought. >> >> If that's not possible, does it make sense to add a note in the docs >> Kernel.SpecialForms.&/1 >> # Capture >> <https://hexdocs.pm/elixir/1.16.2/Kernel.SpecialForms.html#&/1-capture> >> about >> the performance implications of local capture vs external or a >> recommendation? >> >> Thanks. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "elixir-lang-core" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to elixir-lang-co...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/elixir-lang-core/c7065947-b48d-43e6-a450-387f6d4f1846n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/elixir-lang-core/c7065947-b48d-43e6-a450-387f6d4f1846n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/7888d9f2-6aba-4c62-b70b-19581305c15bn%40googlegroups.com.
