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

9 files changed, 174 insertions, 26 deletions

diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 2b7a3b85e5..90f2de594b 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -1604,6 +1604,12 @@ true</pre>
             the form <c>{garbage_collect,
             <anno>RequestId</anno>, <anno>GCResult</anno>}</c>.
           </item>
+
+          <tag><c>{type, 'major' | 'minor'}</c></tag>
+          <item>Triggers garbage collection of requested type. Default value is
+            <c>'major'</c>, which would trigger a fullsweep GC.
+            The option <c>'minor'</c> is considered a hint and may lead to
+            either minor or major GC run.</item>
         </taglist>
         <p>If <c><anno>Pid</anno></c> equals <c>self()</c>, and
           no <c>async</c> option has been passed, the garbage
diff --git a/erts/emulator/beam/atom.names b/erts/emulator/beam/atom.names
index badd69856e..f88aeba49f 100644
--- a/erts/emulator/beam/atom.names
+++ b/erts/emulator/beam/atom.names
@@ -361,6 +361,7 @@ atom long_schedule
 atom low
 atom Lt='<'
 atom machine
+atom major
 atom match
 atom match_limit
 atom match_limit_recursion
@@ -388,6 +389,7 @@ atom microstate_accounting
 atom milli_seconds
 atom min_heap_size
 atom min_bin_vheap_size
+atom minor
 atom minor_version
 atom Minus='-'
 atom module
diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c
index d9048065c8..84eab5f651 100644
--- a/erts/emulator/beam/bif.c
+++ b/erts/emulator/beam/bif.c
@@ -3869,7 +3869,24 @@ BIF_RETTYPE garbage_collect_0(BIF_ALIST_0)
 {
     FLAGS(BIF_P) |= F_NEED_FULLSWEEP;
     erts_garbage_collect(BIF_P, 0, NULL, 0);
-    BIF_RET(am_true);
+    return am_true;
+}
+
+/*
+ * Pass atom 'minor' for relaxed generational GC run. This is only
+ * recommendation, major run may still be chosen by VM.
+ * Pass atom 'major' for default behaviour - major GC run (fullsweep)
+ */
+BIF_RETTYPE
+erts_internal_garbage_collect_1(BIF_ALIST_1)
+{
+    switch (BIF_ARG_1) {
+    case am_minor:  break;
+    case am_major:  FLAGS(BIF_P) |= F_NEED_FULLSWEEP; break;
+    default:        BIF_ERROR(BIF_P, BADARG);
+    }
+    erts_garbage_collect(BIF_P, 0, NULL, 0);
+    return am_true;
 }
 
 /**********************************************************************/
diff --git a/erts/emulator/beam/bif.tab b/erts/emulator/beam/bif.tab
index 978bcd4bba..5bb7db5d47 100644
--- a/erts/emulator/beam/bif.tab
+++ b/erts/emulator/beam/bif.tab
@@ -69,6 +69,7 @@ bif erlang:float_to_list/1
 bif erlang:float_to_list/2
 bif erlang:fun_info/2
 bif erlang:garbage_collect/0
+bif erts_internal:garbage_collect/1
 bif erlang:get/0
 bif erlang:get/1
 bif erlang:get_keys/1
diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index 85c37e08be..a0c5e247d4 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -446,7 +446,8 @@ int erts_system_profile_ts_type = ERTS_TRACE_FLG_NOW_TIMESTAMP;
 #endif
 
 typedef enum {
-    ERTS_PSTT_GC,	/* Garbage Collect */
+    ERTS_PSTT_GC_MAJOR,	/* Garbage Collect: Fullsweep */
+    ERTS_PSTT_GC_MINOR,	/* Garbage Collect: Generational */
     ERTS_PSTT_CPC,	/* Check Process Code */
     ERTS_PSTT_COHMQ,    /* Change off heap message queue */
     ERTS_PSTT_FTMQ      /* Flush trace msg queue */
@@ -10358,7 +10359,8 @@ execute_sys_tasks(Process *c_p, erts_aint32_t *statep, int in_reds)
 	    break;
 
 	switch (st->type) {
-	case ERTS_PSTT_GC:
+        case ERTS_PSTT_GC_MAJOR:
+        case ERTS_PSTT_GC_MINOR:
 	    if (c_p->flags & F_DISABLE_GC) {
 		save_gc_task(c_p, st, st_prio);
 		st = NULL;
@@ -10366,7 +10368,9 @@ execute_sys_tasks(Process *c_p, erts_aint32_t *statep, int in_reds)
 	    }
 	    else {
 		if (!garbage_collected) {
-		    FLAGS(c_p) |= F_NEED_FULLSWEEP;
+                    if (st->type == ERTS_PSTT_GC_MAJOR) {
+                        FLAGS(c_p) |= F_NEED_FULLSWEEP;
+                    }
 		    reds -= scheduler_gc_proc(c_p, reds);
 		    garbage_collected = 1;
 		}
@@ -10442,7 +10446,8 @@ cleanup_sys_tasks(Process *c_p, erts_aint32_t in_state, int in_reds)
 	    break;
 
 	switch (st->type) {
-	case ERTS_PSTT_GC:
+        case ERTS_PSTT_GC_MAJOR:
+        case ERTS_PSTT_GC_MINOR:
 	    st_res = am_false;
 	    break;
 	case ERTS_PSTT_CPC:
@@ -10555,9 +10560,13 @@ erts_internal_request_system_task_3(BIF_ALIST_3)
     switch (req_type) {
 
     case am_garbage_collect:
-	st->type = ERTS_PSTT_GC;
-	noproc_res = am_false;
-	if (!rp)
+        switch (st->arg[0]) {
+        case am_minor:  st->type = ERTS_PSTT_GC_MINOR; break;
+        case am_major:  st->type = ERTS_PSTT_GC_MAJOR; break;
+        default: goto badarg;
+        }
+        noproc_res = am_false;
+        if (!rp)
 	    goto noproc;
 	break;
 
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index 879daaca0a..801d43e957 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -811,6 +811,10 @@ call_ext u==0 Bif=u$bif:erlang:garbage_collect/0 => i_call_ext Bif
 call_ext_last u==0 Bif=u$bif:erlang:garbage_collect/0 D => i_call_ext_last Bif D
 call_ext_only u==0 Bif=u$bif:erlang:garbage_collect/0 => i_call_ext_only Bif
 
+call_ext u==1 Bif=u$bif:erts_internal:garbage_collect/1 => i_call_ext Bif
+call_ext_last u==1 Bif=u$bif:erts_internal:garbage_collect/1 D => i_call_ext_last Bif D
+call_ext_only u==1 Bif=u$bif:erts_internal:garbage_collect/1 => i_call_ext_only Bif
+
 #
 # put/2 and erase/1 must be able to do garbage collection, so we must call
 # them like functions.
diff --git a/erts/emulator/test/gc_SUITE.erl b/erts/emulator/test/gc_SUITE.erl
index 8a600b7d9f..35dd147550 100644
--- a/erts/emulator/test/gc_SUITE.erl
+++ b/erts/emulator/test/gc_SUITE.erl
@@ -23,15 +23,26 @@
 -module(gc_SUITE).
 
 -include_lib("common_test/include/ct.hrl").
+-include_lib("eunit/include/eunit.hrl").
+
 -export([all/0, suite/0]).
 
--export([grow_heap/1, grow_stack/1, grow_stack_heap/1, max_heap_size/1]).
+-export([
+    grow_heap/1,
+    grow_stack/1,
+    grow_stack_heap/1,
+    max_heap_size/1,
+    minor_major_gc_option_async/1,
+    minor_major_gc_option_self/1
+]).
 
 suite() ->
     [{ct_hooks,[ts_install_cth]}].
 
 all() -> 
-    [grow_heap, grow_stack, grow_stack_heap, max_heap_size].
+    [grow_heap, grow_stack, grow_stack_heap, max_heap_size,
+    minor_major_gc_option_self,
+    minor_major_gc_option_async].
 
 
 %% Produce a growing list of elements,
@@ -190,3 +201,91 @@ long_receive() ->
     after 10000 ->
             ok
     end.
+
+minor_major_gc_option_self(_Config) ->
+    Endless = fun Endless() ->
+                receive
+                    {gc, Type} -> erlang:garbage_collect(self(), [{type, Type}])
+                    after 100 -> ok end,
+                Endless()
+              end,
+
+    %% Try as major, a test process will self-trigger GC
+    P1 = spawn(Endless),
+    erlang:garbage_collect(P1, []),
+    erlang:trace(P1, true, [garbage_collection]),
+    P1 ! {gc, major},
+    expect_trace_messages(P1, [gc_major_start, gc_major_end]),
+    erlang:trace(P1, false, [garbage_collection]),
+    erlang:exit(P1, kill),
+
+    %% Try as minor, a test process will self-trigger GC
+    P2 = spawn(Endless),
+    erlang:garbage_collect(P2, []),
+    erlang:trace(P2, true, [garbage_collection]),
+    P2 ! {gc, minor},
+    expect_trace_messages(P2, [gc_minor_start, gc_minor_end]),
+    erlang:trace(P2, false, [garbage_collection]),
+    erlang:exit(P2, kill).
+
+minor_major_gc_option_async(_Config) ->
+    Endless = fun Endless() ->
+                  receive after 100 -> ok end,
+                  Endless()
+              end,
+
+    %% Try with default option, must be major gc
+    P1 = spawn(Endless),
+    erlang:garbage_collect(P1, []),
+    erlang:trace(P1, true, [garbage_collection]),
+    erlang:garbage_collect(P1, []),
+    expect_trace_messages(P1, [gc_major_start, gc_major_end]),
+    erlang:trace(P1, false, [garbage_collection]),
+    erlang:exit(P1, kill),
+
+    %% Try with the 'major' type
+    P2 = spawn(Endless),
+    erlang:garbage_collect(P2, []),
+    erlang:trace(P2, true, [garbage_collection]),
+    erlang:garbage_collect(P2, [{type, major}]),
+    expect_trace_messages(P2, [gc_major_start, gc_major_end]),
+    erlang:trace(P2, false, [garbage_collection]),
+    erlang:exit(P2, kill),
+
+    %% Try with 'minor' option, once
+    P3 = spawn(Endless),
+    erlang:garbage_collect(P3, []),
+    erlang:trace(P3, true, [garbage_collection]),
+    erlang:garbage_collect(P3, [{type, minor}]),
+    expect_trace_messages(P3, [gc_minor_start, gc_minor_end]),
+    erlang:trace(P3, false, [garbage_collection]),
+    erlang:exit(P3, kill),
+
+    %% Try with 'minor' option, once, async
+    P4 = spawn(Endless),
+    Ref = erlang:make_ref(),
+    erlang:garbage_collect(P4, []),
+    erlang:trace(P4, true, [garbage_collection]),
+    ?assertEqual(async,
+                 erlang:garbage_collect(P4, [{type, minor}, {async, Ref}])),
+    expect_trace_messages(P4, [gc_minor_start, gc_minor_end]),
+    erlang:trace(P4, false, [garbage_collection]),
+    receive {garbage_collect, Ref, true} -> ok;
+        Other4 -> ct:pal("Unexpected message: ~p~n"
+                         ++ "while waiting for async gc result", [Other4])
+    after 2000 -> ?assert(false)
+    end,
+    erlang:exit(P4, kill).
+
+%% Given a list of atoms, trace tags - receives messages and checks if they are
+%% trace events, and if the tag matches. Else will crash failing the test.
+expect_trace_messages(_Pid, []) -> ok;
+expect_trace_messages(Pid, [Tag | TraceTags]) ->
+    receive
+        {trace, Pid, Tag, _Data} -> ok;
+        AnythingElse ->
+            ct:pal("Unexpected message: ~p~nWhile expected {trace, _, ~p, _}",
+                   [AnythingElse, Tag]),
+            ?assert(false)
+    end,
+    expect_trace_messages(Pid, TraceTags).
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)).