Merge pull request #9342 from bjorng/bjorn/erts/booting/OTP-19450

Limit peak memory use while loading code on small systems
erlang · Jan 28, 2025 · a0a606b · a0a606b
2 parents 1b2af94 + 1c80658
commit a0a606b
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Showing 5 changed files with 31 additions and 7 deletions.
diff --git a/erts/preloaded/ebin/erl_prim_loader.beam b/erts/preloaded/ebin/erl_prim_loader.beam
diff --git a/erts/preloaded/ebin/init.beam b/erts/preloaded/ebin/init.beam
diff --git a/erts/preloaded/src/erl_prim_loader.erl b/erts/preloaded/src/erl_prim_loader.erl
@@ -483,6 +483,7 @@ loop(St0, Parent, Paths) ->
 		    ok;
 		{Resp,#state{}=St1} ->
 		    Pid ! {self(),Resp},
+                    erlang:garbage_collect(),
                     loop(St1, Parent, Paths);
 		{_,State2,_} ->
                     exit({bad_state,Req,State2})
@@ -691,18 +692,20 @@ efile_gm_recv(N, Ref, Succ, Fail) ->
     end.
 
 efile_gm_spawn(ParentRef, Ms, Process, Paths) ->
-    efile_gm_spawn_1(0, Ms, ParentRef, Process, Paths).
+    S = erlang:system_info(schedulers_online),
+    MaxN = min(S + (S bsr 1), 32),
+    efile_gm_spawn_1(0, MaxN, Ms, ParentRef, Process, Paths).
 
-efile_gm_spawn_1(N, Ms, ParentRef, Process, Paths) when N >= 32 ->
+efile_gm_spawn_1(N, MaxN, Ms, ParentRef, Process, Paths) when N > MaxN ->
     receive
 	{'DOWN',_,process,_,_} ->
-	    efile_gm_spawn_1(N-1, Ms, ParentRef, Process, Paths)
+	    efile_gm_spawn_1(N-1, MaxN, Ms, ParentRef, Process, Paths)
     end;
-efile_gm_spawn_1(N, [M|Ms], ParentRef, Process, Paths) ->
+efile_gm_spawn_1(N, MaxN, [M|Ms], ParentRef, Process, Paths) ->
     Get = fun() -> efile_gm_get(Paths, M, ParentRef, Process) end,
     _ = spawn_monitor(Get),
-    efile_gm_spawn_1(N+1, Ms, ParentRef, Process, Paths);
-efile_gm_spawn_1(_, [], _, _, _) ->
+    efile_gm_spawn_1(N+1, MaxN, Ms, ParentRef, Process, Paths);
+efile_gm_spawn_1(_, _, [], _, _, _) ->
     ok.
 
 efile_gm_get(Paths, Mod, ParentRef, Process) ->

diff --git a/erts/preloaded/src/init.erl b/erts/preloaded/src/init.erl
@@ -1359,6 +1359,18 @@ eval_script(What, #es{}) ->
 load_modules(Mods0, Init) ->
     Mods = [M || M <- Mods0, not erlang:module_loaded(M)],
     F = prepare_loading_fun(),
+    case has_small_memory() of
+        true ->
+            %% Load one module at the time to reduce the peak memory
+            %% usage.
+            _ = [do_load_modules([M], F, Init) || M <- Mods],
+            ok;
+        false ->
+            %% Load the modules in parallel.
+            do_load_modules(Mods, F, Init)
+    end.
+
+do_load_modules(Mods, F, Init) ->
     case erl_prim_loader:get_modules(Mods, F) of
 	{ok,{Prep0,[]}} ->
 	    Prep = [Code || {_,{prepared,Code,_}} <- Prep0],
@@ -1394,6 +1406,13 @@ prepare_loading_fun() ->
 	    end
     end.
 
+has_small_memory() ->
+    %% Heuristic for small memory. If true, we'll try to preserve
+    %% memory by not loading code in parallel.
+    (erlang:system_info(wordsize) =:= 4 andalso
+     erlang:system_info(schedulers_online) =:= 1) orelse
+        erlang:system_info(debug_compiled).
+
 make_path(Pa, Pz, Path, Vars) ->
     append([Pa,append([fix_path(Path,Vars),Pz])]).
 

diff --git a/lib/kernel/src/code.erl b/lib/kernel/src/code.erl
@@ -569,7 +569,9 @@ ensure_loaded(Mod) when is_atom(Mod) ->
                                     call({load_error, Mod, Ref}),
                                     Error;
                                 Prepared ->
-                                    call({load_ok, Prepared, Mod, File, Ref})
+                                    Res = call({load_ok, Prepared, Mod, File, Ref}),
+                                    erlang:garbage_collect(),
+                                    Res
                             end
                     end;
                 embedded ->