Option to erlang:garbage_collect to request minor (generational) GC

Note: Minor GC option is a hint, and GC may still decide to run fullsweep.
Test case for major and minor gc on self
Test case for major and minor gs on some other process + async gc test check

docs fix

2 files changed, 26 insertions, 16 deletions

diff --git a/erts/preloaded/src/erlang.erl b/erts/preloaded/src/erlang.erl
index edf79b8f75..dd1156f292 100644
--- a/erts/preloaded/src/erlang.erl
+++ b/erts/preloaded/src/erlang.erl
@@ -875,36 +875,39 @@ garbage_collect(Pid) ->
 	error:Error -> erlang:error(Error, [Pid])
     end.
 
+-record(gcopt, {
+    async = sync :: sync | {async, _},
+    type = major % default major, can also be minor
+    }).
+
 %% garbage_collect/2
 -spec garbage_collect(Pid, OptionList) -> GCResult | async when
       Pid :: pid(),
       RequestId :: term(),
-      Option :: {async, RequestId},
+      Option :: {async, RequestId} | {type, 'major' | 'minor'},
       OptionList :: [Option],
       GCResult :: boolean().
 garbage_collect(Pid, OptionList)  ->
     try
-	Async = get_gc_opts(OptionList, sync),
-	case Async of
+	GcOpts = get_gc_opts(OptionList, #gcopt{}),
+	case GcOpts#gcopt.async of
 	    {async, ReqId} ->
 		{priority, Prio} = erlang:process_info(erlang:self(),
 						       priority),
-		erts_internal:request_system_task(Pid,
-						  Prio,
-						  {garbage_collect, ReqId}),
+		erts_internal:request_system_task(
+                    Pid, Prio, {garbage_collect, ReqId, GcOpts#gcopt.type}),
 		async;
 	    sync ->
 		case Pid == erlang:self() of
 		    true ->
-			erlang:garbage_collect();
+			erts_internal:garbage_collect(GcOpts#gcopt.type);
 		    false ->
 			{priority, Prio} = erlang:process_info(erlang:self(),
 							       priority),
 			ReqId = erlang:make_ref(),
-			erts_internal:request_system_task(Pid,
-							  Prio,
-							  {garbage_collect,
-							   ReqId}),
+			erts_internal:request_system_task(
+                            Pid, Prio,
+                            {garbage_collect, ReqId, GcOpts#gcopt.type}),
 			receive
 			    {garbage_collect, ReqId, GCResult} ->
 				GCResult
@@ -916,10 +919,12 @@ garbage_collect(Pid, OptionList)  ->
     end.
 
 % gets async opt and verify valid option list
-get_gc_opts([{async, _ReqId} = AsyncTuple | Options], _OldAsync) ->
-    get_gc_opts(Options, AsyncTuple);
-get_gc_opts([], Async) ->
-    Async.
+get_gc_opts([{async, _ReqId} = AsyncTuple | Options], GcOpt = #gcopt{}) ->
+    get_gc_opts(Options, GcOpt#gcopt{ async = AsyncTuple });
+get_gc_opts([{type, T} | Options], GcOpt = #gcopt{}) ->
+    get_gc_opts(Options, GcOpt#gcopt{ type = T });
+get_gc_opts([], GcOpt) ->
+    GcOpt.
 
 %% garbage_collect_message_area/0
 -spec erlang:garbage_collect_message_area() -> boolean().
diff --git a/erts/preloaded/src/erts_internal.erl b/erts/preloaded/src/erts_internal.erl
index 2459ea2a2c..6f2e50d1db 100644
--- a/erts/preloaded/src/erts_internal.erl
+++ b/erts/preloaded/src/erts_internal.erl
@@ -38,7 +38,8 @@
 -export([system_check/1,
          gather_system_check_result/1]).
 
--export([request_system_task/3]).
+-export([request_system_task/3,
+         garbage_collect/1]).
 
 -export([check_process_code/3]).
 -export([copy_literals/2]).
@@ -210,6 +211,10 @@ port_info(_Result, _Item) ->
 request_system_task(_Pid, _Prio, _Request) ->
     erlang:nif_error(undefined).
 
+-spec garbage_collect(Mode) -> 'true' when Mode :: 'major' | 'minor'.
+garbage_collect(_Mode) ->
+    erlang:nif_error(undefined).
+
 -define(ERTS_CPC_ALLOW_GC, (1 bsl 0)).
 -define(ERTS_CPC_COPY_LITERALS, (1 bsl 1)).