perf(gateway): restore generational GC as the vm default (#2181)

fluxer_gateway/src/gateway/fluxer_gateway_app.erl

@@ -7,7 +7,7 @@
 
 -spec start(application:start_type(), term()) -> {ok, pid()} | {error, term()}.
 start(_StartType, _StartArgs) ->
-    erlang:system_flag(fullsweep_after, 0),
+    erlang:system_flag(fullsweep_after, 10),
     init_jose(),
     init_subsystems(),
     {ok, Pid} = fluxer_gateway_sup:start_link(),

fluxer_gateway/test/fluxer_gateway_app_tests.erl

@@ -0,0 +1,28 @@
+%% SPDX-License-Identifier: AGPL-3.0-or-later
+
+-module(fluxer_gateway_app_tests).
+-typing([eqwalizer]).
+-include_lib("eunit/include/eunit.hrl").
+
+start_keeps_generational_gc_as_vm_default_test() ->
+    ?assertEqual([10], vm_fullsweep_after_values()).
+
+vm_fullsweep_after_values() ->
+    {fluxer_gateway_app, Beam, _Path} = code:get_object_code(fluxer_gateway_app),
+    {ok, {fluxer_gateway_app, [{abstract_code, {raw_abstract_v1, Forms}}]}} =
+        beam_lib:chunks(Beam, [abstract_code]),
+    collect_fullsweep_after(Forms, []).
+
+collect_fullsweep_after([Form | Rest], Acc) ->
+    collect_fullsweep_after(Rest, collect_fullsweep_after(Form, Acc));
+collect_fullsweep_after(
+    {call, _, {remote, _, {atom, _, erlang}, {atom, _, system_flag}}, [
+        {atom, _, fullsweep_after}, {integer, _, Value}
+    ]},
+    Acc
+) ->
+    Acc ++ [Value];
+collect_fullsweep_after(Form, Acc) when is_tuple(Form) ->
+    collect_fullsweep_after(tuple_to_list(Form), Acc);
+collect_fullsweep_after(_Form, Acc) ->
+    Acc.