From a51fea68bbcf341bf7857a6bd3f0c17ffd0402bb Mon Sep 17 00:00:00 2001
From: Ingela Anderton Andin <ingela@erlang.org>
Date: Tue, 15 Feb 2011 16:51:38 +0100
Subject: Do not save parameter list for any temporary processes

Previous commit changed the supervisor to not save
parameter lists for temporary processes supervised by simple-one-for-one
supervisors. But it is unnecessary to save them for any
temporary processes as they should not be restarted. Proably the
biggest gain is in the simple-one-for-one case.

Also changed the test case count_children_memory so it does
not test that which_children will produce garbage that must
be reclaimed later. This is a strange thing to test and it is no
longer true for all invocations of which_children.
---
 lib/stdlib/src/supervisor.erl        | 25 ++++++++++++++++---------
 lib/stdlib/test/supervisor_SUITE.erl | 20 ++++----------------
 2 files changed, 20 insertions(+), 25 deletions(-)

diff --git a/lib/stdlib/src/supervisor.erl b/lib/stdlib/src/supervisor.erl
index bfa7c96eca..469063689d 100644
--- a/lib/stdlib/src/supervisor.erl
+++ b/lib/stdlib/src/supervisor.erl
@@ -562,15 +562,11 @@ handle_start_child(Child, State) ->
 	false ->
 	    case do_start_child(State#state.name, Child) of
 		{ok, Pid} ->
-		    Children = State#state.children,
 		    {{ok, Pid},
-		     State#state{children = 
-				 [Child#child{pid = Pid}|Children]}};
+		     save_child(Child#child{pid = Pid}, State)};
 		{ok, Pid, Extra} ->
-		    Children = State#state.children,
 		    {{ok, Pid, Extra},
-		     State#state{children = 
-				 [Child#child{pid = Pid}|Children]}};
+		     save_child(Child#child{pid = Pid}, State)};
 		{error, What} ->
 		    {{error, {What, Child}}, State}
 	    end;
@@ -593,13 +589,13 @@ restart_child(Pid, Reason, #state{children = [Child]} = State) when ?is_simple(S
 	    NChild = Child#child{pid = Pid, mfargs = {M, F, Args}},
 	    do_restart(RestartType, Reason, NChild, State);
 	error ->
-	    {ok, State}
+            {ok, State}
     end;
+
 restart_child(Pid, Reason, State) ->
     Children = State#state.children,
     case lists:keyfind(Pid, #child.pid, Children) of
-	#child{} = Child ->
-	    RestartType = Child#child.restart_type,
+	#child{restart_type = RestartType} = Child ->
 	    do_restart(RestartType, Reason, Child, State);
 	false ->
 	    {ok, State}
@@ -783,6 +779,17 @@ monitor_child(Pid) ->
 %% Child/State manipulating functions.
 %%-----------------------------------------------------------------
 
+%% Note we do not want to save the parameter list for temporary processes as
+%% they will not be restarted, and hence we do not need this information.
+%% Especially for dynamic children to simple_one_for_one supervisors
+%% it could become very costly as it is not uncommon to spawn
+%% very many such processes.
+save_child(#child{restart_type = temporary,
+		  mfargs = {M, F, _}} = Child, #state{children = Children} = State) ->
+    State#state{children = [Child#child{mfargs = {M, F, undefined}} |Children]};
+save_child(Child, #state{children = Children} = State) ->
+    State#state{children = [Child |Children]}.
+
 save_dynamic_child(temporary, Pid, _, #state{dynamics = Dynamics} = State) ->
     State#state{dynamics = [Pid | dynamics_db(temporary, Dynamics)]};
 save_dynamic_child(RestartType, Pid, Args, #state{dynamics = Dynamics} = State) ->
diff --git a/lib/stdlib/test/supervisor_SUITE.erl b/lib/stdlib/test/supervisor_SUITE.erl
index 039ea298c4..4708658a6d 100644
--- a/lib/stdlib/test/supervisor_SUITE.erl
+++ b/lib/stdlib/test/supervisor_SUITE.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 1996-2010. All Rights Reserved.
+%% Copyright Ericsson AB 1996-2011. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -1279,7 +1279,7 @@ count_children_allocator_test(MemoryState) ->
     lists:all(fun(State) -> State == {e, true} end, AllocStates).
 
 count_children_memory(doc) ->
-    ["Test that which_children eats memory, but count_children does not."];
+    ["Test that count_children does not eat memory."];
 count_children_memory(suite) ->
     MemoryState = erlang:system_info(allocator),
     case count_children_allocator_test(MemoryState) of
@@ -1323,8 +1323,8 @@ count_children_memory(Config) when is_list(Config) ->
     ?line ChildCount3 = ChildCount2,
 
     %% count_children consumes memory using an accumulator function,
-    %% but the space can be reclaimed incrementally, whereas
-    %% which_children generates a return list.
+    %% but the space can be reclaimed incrementally,
+    %% which_children may generate garbage that will reclaimed later.
     case (Size5 =< Size4) of
 	true -> ok;
 	false ->
@@ -1336,19 +1336,7 @@ count_children_memory(Config) when is_list(Config) ->
 	    ?line test_server:fail({count_children, used_more_memory})
     end,
 
-    case Size4 > Size3 of
-	true -> ok;
-	false ->
-	    ?line test_server:fail({which_children, used_no_memory})
-    end,
-    case Size6 > Size5 of
-	true -> ok;
-	false ->
-	    ?line test_server:fail({which_children, used_no_memory})
-    end,
-
     [exit(Pid, kill) || {undefined, Pid, worker, _Modules} <- Children3],
     test_server:sleep(100),
     ?line [1,0,0,0] = get_child_counts(sup_test),
-
     ok.
-- 
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