Fragmented young heap generation and off_heap_message_queue option

* The youngest generation of the heap can now consist of multiple
  blocks. Heap fragments and message fragments are added to the
  youngest generation when needed without triggering a GC. After
  a GC the youngest generation is contained in one single block.
* The off_heap_message_queue process flag has been added. When
  enabled all message data in the queue is kept off heap. When
  a message is selected from the queue, the message fragment (or
  heap fragment) containing the actual message is attached to the
  youngest generation. Messages stored off heap is not part of GC.

1 files changed, 20 insertions, 24 deletions

diff --git a/erts/preloaded/src/erlang.erl b/erts/preloaded/src/erlang.erl
index 291356c7b1..e46d64eb0a 100644
--- a/erts/preloaded/src/erlang.erl
+++ b/erts/preloaded/src/erlang.erl
@@ -2044,6 +2044,9 @@ open_port(_PortName,_PortSettings) ->
                   (min_bin_vheap_size, MinBinVHeapSize) -> OldMinBinVHeapSize when
       MinBinVHeapSize :: non_neg_integer(),
       OldMinBinVHeapSize :: non_neg_integer();
+                  (off_heap_message_queue, OHMQ) -> OldOHMQ when
+      OHMQ :: boolean(),
+      OldOHMQ :: boolean();
                   (priority, Level) -> OldLevel when
       Level :: priority_level(),
       OldLevel :: priority_level();
@@ -2082,6 +2085,7 @@ process_flag(_Flag, _Value) ->
       min_bin_vheap_size |
       monitored_by |
       monitors |
+      off_heap_message_queue |
       priority |
       reductions |
       registered_name |
@@ -2123,6 +2127,7 @@ process_flag(_Flag, _Value) ->
       {monitors,
        Monitors :: [{process, Pid :: pid() |
                                      {RegName :: atom(), Node :: node()}}]} |
+      {off_heap_message_queue, OHMQ :: boolean()} |
       {priority, Level :: priority_level()} |
       {reductions, Number :: non_neg_integer()} |
       {registered_name, Atom :: atom()} |
@@ -2425,6 +2430,7 @@ tuple_to_list(_Tuple) ->
          (multi_scheduling) -> disabled | blocked | enabled;
          (multi_scheduling_blockers) -> [PID :: pid()];
          (nif_version) -> string();
+         (off_heap_message_queue) -> boolean();
          (otp_release) -> string();
          (os_monotonic_time_source) -> [{atom(),term()}];
          (os_system_time_source) -> [{atom(),term()}];
@@ -2552,14 +2558,19 @@ spawn_monitor(M, F, A) when erlang:is_atom(M),
 spawn_monitor(M, F, A) ->
     erlang:error(badarg, [M,F,A]).
 
+
+-type spawn_opt_option() ::
+	link
+      | monitor
+      | {priority, Level :: priority_level()}
+      | {fullsweep_after, Number :: non_neg_integer()}
+      | {min_heap_size, Size :: non_neg_integer()}
+      | {min_bin_vheap_size, VSize :: non_neg_integer()}
+      | {off_heap_message_queue, OHMQ :: boolean()}.
+
 -spec spawn_opt(Fun, Options) -> pid() | {pid(), reference()} when
       Fun :: function(),
-      Options :: [Option],
-      Option :: link | monitor
-              | {priority, Level :: priority_level()}
-              | {fullsweep_after, Number :: non_neg_integer()}
-              | {min_heap_size, Size :: non_neg_integer()}
-              | {min_bin_vheap_size, VSize :: non_neg_integer()}.
+      Options :: [spawn_opt_option()].
 spawn_opt(F, O) when erlang:is_function(F) ->
     spawn_opt(erlang, apply, [F, []], O);
 spawn_opt({M,F}=MF, O) when erlang:is_atom(M), erlang:is_atom(F) ->
@@ -2572,12 +2583,7 @@ spawn_opt(F, O) ->
 -spec spawn_opt(Node, Fun, Options) -> pid() | {pid(), reference()} when
       Node :: node(),
       Fun :: function(),
-      Options :: [Option],
-      Option :: link | monitor
-              | {priority, Level :: priority_level()}
-              | {fullsweep_after, Number :: non_neg_integer()}
-              | {min_heap_size, Size :: non_neg_integer()}
-              | {min_bin_vheap_size, VSize :: non_neg_integer()}.
+      Options :: [spawn_opt_option()].
 spawn_opt(N, F, O) when N =:= erlang:node() ->
     spawn_opt(F, O);
 spawn_opt(N, F, O) when erlang:is_function(F) ->
@@ -2664,12 +2670,7 @@ spawn_link(N,M,F,A) ->
       Module :: module(),
       Function :: atom(),
       Args :: [term()],
-      Options :: [Option],
-      Option :: link | monitor
-              | {priority, Level :: priority_level()}
-              | {fullsweep_after, Number :: non_neg_integer()}
-              | {min_heap_size, Size :: non_neg_integer()}
-              | {min_bin_vheap_size, VSize :: non_neg_integer()}.
+      Options :: [spawn_opt_option()].
 spawn_opt(M, F, A, Opts) ->
     case catch erlang:spawn_opt({M,F,A,Opts}) of
 	{'EXIT',{Reason,_}} ->
@@ -2684,12 +2685,7 @@ spawn_opt(M, F, A, Opts) ->
       Module :: module(),
       Function :: atom(),
       Args :: [term()],
-      Options :: [Option],
-      Option :: link | monitor
-              | {priority, Level :: priority_level()}
-              | {fullsweep_after, Number :: non_neg_integer()}
-              | {min_heap_size, Size :: non_neg_integer()}
-              | {min_bin_vheap_size, VSize :: non_neg_integer()}.
+      Options :: [spawn_opt_option()].
 spawn_opt(N, M, F, A, O) when N =:= erlang:node(),
 			      erlang:is_atom(M), erlang:is_atom(F),
                               erlang:is_list(A), erlang:is_list(O) ->