The use of String.split instead of :binary.split seems excessive here. Could be a small but quick win.
On Tue, Aug 18, 2020 at 9:03 AM José Valim <jose.va...@dashbit.co> wrote: > We need to go route 2, as 1 can change at any time (including if 2 is > implemented). So thank you for opening an issue on Erlang's issues tracker, > I am now watching it and I can act based on its status. :) > > On Mon, Aug 17, 2020 at 11:45 PM Trevor Brown <ad...@stratus3d.com> wrote: > >> Background >> >> I was recently working on a project that invoked `System.get_env/0` on >> every request it handled. Someone changed the infrastructure the >> application was deployed on and greatly increased the number of environment >> variables (3x more) in the environment the Elixir application ran in, and >> the performance of the application degraded by about that same amount (3x >> slower than before). When I profiled the application I quickly found that >> most of the request handling was spent waiting for the `System.get_env/0` >> function to return. I changed the code so `System.get_env/0` was only >> invoked on startup and the performance issue was resolved. >> >> Problem >> >> When I was working on the performance issue in the app the flame graphs >> revealed something interesting - Erlang was actually formatting the >> environment variables from a proplist to a list of strings in certain >> format, and then Elixir was undoing the formatting by parsing the strings >> back to a map! Because of this the performance of the `System.get_env/0` >> function call is tied to the number of variables in the environment. >> >> >> - The Erlang code that formats the variables: >> https://github.com/erlang/otp/blob/master/lib/kernel/src/os.erl#L118 >> - The Elixir code that parses them and puts them in a dictionary: >> >> https://github.com/elixir-lang/elixir/blob/v1.10.3/lib/elixir/lib/system.ex#L438 >> >> >> Possible Solutions >> >> *1. Update the `System.get_env/0` function to use `os:list_env_vars/0` >> function* >> >> This function already exists returns a proplists in the format >> `{VariableName, VariableValue}`. All we need to do is replace the existing >> code with >> >> def get_env do >> Enum.into(:os.list_env_vars(), %{}) >> end >> >> This would solve the performance issue and simplify the Elixir code! The >> downside is that `os:list_env_vars/0` is not a documented function, which I >> assume means it's not recommended for other applications to rely on it. >> >> *2. Wait for Erlang to change* >> >> Because I assumed `os:list_env_vars/0` is not a function that Elixir >> should be relying on (although nothing prevents it from doing so), I have >> created an enhancement ticket on the Erlang issue tracker to document >> `os:list_env_vars/0` or implement another function that returns the >> environment variables in a proplist with `{VariableName, VariableValue}` >> tuples - https://bugs.erlang.org/browse/ERL-1332. >> <https://bugs.erlang.org/browse/ERL-1332> Once Erlang implements a >> documented function that does this we could then begin updating Elixir. >> >> Thoughts? I doubt this is something that is run into very often but it >> could be easily improved. >> >> -- >> 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/0aecb090-2cbb-46af-8ff4-e34337b123d4o%40googlegroups.com >> <https://groups.google.com/d/msgid/elixir-lang-core/0aecb090-2cbb-46af-8ff4-e34337b123d4o%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/CAGnRm4KHzHHTw_mU6vCUoK3yPYT5cQQBWicMkQ5cGTpZTmT26Q%40mail.gmail.com > <https://groups.google.com/d/msgid/elixir-lang-core/CAGnRm4KHzHHTw_mU6vCUoK3yPYT5cQQBWicMkQ5cGTpZTmT26Q%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- Best regards Alexei Sholik -- 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/CAAPY6eMy9APxCjX5OCjdrKEByQTzzPQ4NMWQJuNCXzuXO-Xtyw%40mail.gmail.com.
