Introduce a new time API

The old time API is based on erlang:now/0. The major issue with
erlang:now/0 is that it was intended to be used for so many
unrelated things. This tied these unrelated operations together
and unnecessarily caused performance, scalability as well as
accuracy, and precision issues for operations that do not need
to have such issues. The new API spreads different functionality
over multiple functions in order to improve on this.

The new API consists of a number of new BIFs:
- erlang:convert_time_unit/3
- erlang:monotonic_time/0
- erlang:monotonic_time/1
- erlang:system_time/0
- erlang:system_time/1
- erlang:time_offset/0
- erlang:time_offset/1
- erlang:timestamp/0
- erlang:unique_integer/0
- erlang:unique_integer/1
- os:system_time/0
- os:system_time/1

and a number of extensions of existing BIFs:
- erlang:monitor(time_offset, clock_service)
- erlang:system_flag(time_offset, finalize)
- erlang:system_info(os_monotonic_time_source)
- erlang:system_info(time_offset)
- erlang:system_info(time_warp_mode)
- erlang:system_info(time_correction)
- erlang:system_info(start_time)

See the "Time and Time Correction in Erlang" chapter of the
ERTS User's Guide for more information.

5 files changed, 148 insertions, 18 deletions

diff --git a/erts/preloaded/ebin/erlang.beam b/erts/preloaded/ebin/erlang.beam
index 7a3d94dd16..4ec388a7b9 100644
--- a/erts/preloaded/ebin/erlang.beam
+++ b/erts/preloaded/ebin/erlang.beam
diff --git a/erts/preloaded/ebin/erts_internal.beam b/erts/preloaded/ebin/erts_internal.beam
index 9b364d8b21..705bb61247 100644
--- a/erts/preloaded/ebin/erts_internal.beam
+++ b/erts/preloaded/ebin/erts_internal.beam
diff --git a/erts/preloaded/ebin/init.beam b/erts/preloaded/ebin/init.beam
index a190129b2c..aadc9797cb 100644
--- a/erts/preloaded/ebin/init.beam
+++ b/erts/preloaded/ebin/init.beam
diff --git a/erts/preloaded/src/erlang.erl b/erts/preloaded/src/erlang.erl
index 611a568014..79eb60f362 100644
--- a/erts/preloaded/src/erlang.erl
+++ b/erts/preloaded/src/erlang.erl
@@ -38,7 +38,6 @@
 
 -export([integer_to_list/2]).
 -export([integer_to_binary/2]).
--export([flush_monitor_message/2]).
 -export([set_cpu_topology/1, format_cpu_topology/1]).
 -export([await_proc_exit/3]).
 -export([memory/0, memory/1]).
@@ -48,7 +47,7 @@
 	 await_sched_wall_time_modifications/2,
 	 gather_gc_info_result/1]).
 
--deprecated([hash/2]).
+-deprecated([hash/2, now/0]).
 
 %% Get rid of autoimports of spawn to avoid clashes with ourselves.
 -compile({no_auto_import,[spawn_link/1]}).
@@ -58,12 +57,21 @@
 -compile({no_auto_import,[spawn_opt/5]}).
 
 -export_type([timestamp/0]).
+-export_type([time_unit/0]).
 
 -type ext_binary() :: binary().
 -type timestamp() :: {MegaSecs :: non_neg_integer(),
                       Secs :: non_neg_integer(),
                       MicroSecs :: non_neg_integer()}.
 
+-type time_unit() ::
+	pos_integer()
+      | 'seconds'
+      | 'milli_seconds'
+      | 'micro_seconds'
+      | 'nano_seconds'
+      | 'native'.
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %% Native code BIF stubs and their types
 %% (BIF's actually implemented in this module goes last in the file)
@@ -104,7 +112,8 @@
 -export([list_to_bitstring/1, list_to_existing_atom/1, list_to_float/1]).
 -export([list_to_integer/1, list_to_integer/2]).
 -export([list_to_pid/1, list_to_tuple/1, loaded/0]).
--export([localtime/0, make_ref/0, map_size/1, match_spec_test/3, md5/1, md5_final/1]).
+-export([localtime/0, make_ref/0]).
+-export([map_size/1, match_spec_test/3, md5/1, md5_final/1]).
 -export([md5_init/0, md5_update/2, module_loaded/1, monitor/2]).
 -export([monitor_node/2, monitor_node/3, nif_error/1, nif_error/2]).
 -export([node/0, node/1, now/0, phash/2, phash2/1, phash2/2]).
@@ -112,6 +121,11 @@
 -export([port_connect/2, port_control/3, port_get_data/1]).
 -export([port_set_data/2, port_to_list/1, ports/0]).
 -export([posixtime_to_universaltime/1, pre_loaded/0, prepare_loading/2]).
+-export([monotonic_time/0, monotonic_time/1]).
+-export([system_time/0, system_time/1]).
+-export([convert_time_unit/3]).
+-export([unique_integer/0, unique_integer/1]).
+-export([time_offset/0, time_offset/1, timestamp/0]).
 -export([process_display/2]).
 -export([process_flag/3, process_info/1, processes/0, purge_module/1]).
 -export([put/2, raise/3, read_timer/1, ref_to_list/1, register/2]).
@@ -1184,13 +1198,18 @@ md5_update(_Context, _Data) ->
 module_loaded(_Module) ->
     erlang:nif_error(undefined).
 
+-type registered_name() :: atom().
+
+-type registered_process_identifier() :: registered_name() | {registered_name(), node()}.
+
+-type monitor_process_identifier() :: pid() | registered_process_identifier().
+
 %% monitor/2
--spec monitor(Type, Item) -> MonitorRef when
-      Type :: process,
-      Item :: pid() | RegName | {RegName, Node},
-      RegName :: module(),
-      Node :: node(),
+-spec monitor(process, monitor_process_identifier()) -> MonitorRef when
+      MonitorRef :: reference();
+	     (time_offset, clock_service) -> MonitorRef when
       MonitorRef :: reference().
+
 monitor(_Type, _Item) ->
     erlang:nif_error(undefined).
 
@@ -1292,6 +1311,90 @@ ports() ->
 posixtime_to_universaltime(_P1) ->
     erlang:nif_error(undefined).
 
+-spec erlang:unique_integer(ModifierList) -> integer() when
+      ModifierList :: [Modifier],
+      Modifier :: positive | monotonic.
+
+unique_integer(_ModifierList) ->
+    erlang:nif_error(undefined).
+
+-spec erlang:unique_integer() -> integer().
+
+unique_integer() ->
+    erlang:nif_error(undefined).
+
+-spec erlang:monotonic_time() -> integer().
+
+monotonic_time() ->
+    erlang:nif_error(undefined).
+
+-spec erlang:monotonic_time(Unit) -> integer() when
+      Unit :: time_unit().
+
+monotonic_time(_Unit) ->
+    erlang:nif_error(undefined).
+
+-spec erlang:system_time() -> integer().
+
+system_time() ->
+    erlang:nif_error(undefined).
+
+-spec erlang:system_time(Unit) -> integer() when
+      Unit :: time_unit().
+
+system_time(_Unit) ->
+    erlang:nif_error(undefined).
+
+-spec erlang:convert_time_unit(Time, FromUnit, ToUnit) -> ConvertedTime when
+      Time :: integer(),
+      ConvertedTime :: integer(),
+      FromUnit :: time_unit(),
+      ToUnit :: time_unit().
+
+convert_time_unit(Time, FromUnit, ToUnit) ->
+    try
+	FU = case FromUnit of
+		 native -> erts_internal:time_unit();
+		 nano_seconds -> 1000*1000*1000;
+		 micro_seconds -> 1000*1000;
+		 milli_seconds -> 1000;
+		 seconds -> 1;
+		 _ when FromUnit > 0 -> FromUnit
+	     end,
+	TU = case ToUnit of
+		 native -> erts_internal:time_unit();
+		 nano_seconds -> 1000*1000*1000;
+		 micro_seconds -> 1000*1000;
+		 milli_seconds -> 1000;
+		 seconds -> 1;
+		 _ when ToUnit > 0 -> ToUnit
+	     end,
+	case Time < 0 of
+	    true -> TU*Time - (FU - 1);
+	    false -> TU*Time
+	end div FU
+    catch
+	_ : _ ->
+	    erlang:error(badarg, [Time, FromUnit, ToUnit])
+    end.
+
+-spec erlang:time_offset() -> integer().
+
+time_offset() ->
+    erlang:nif_error(undefined).
+
+-spec erlang:time_offset(Unit) -> integer() when
+      Unit :: time_unit().
+
+time_offset(_Unit) ->
+    erlang:nif_error(undefined).
+
+-spec erlang:timestamp() -> Timestamp when
+      Timestamp :: timestamp().
+
+timestamp() ->
+    erlang:nif_error(undefined).
+
 %% prepare_loading/2
 -spec erlang:prepare_loading(Module, Code) -> PreparedCode | {error, Reason} when
       Module :: module(),
@@ -2118,6 +2221,8 @@ subtract(_,_) ->
                         (trace_control_word, TCW) -> OldTCW when
       TCW :: non_neg_integer(),
       OldTCW :: non_neg_integer();
+			(time_offset, finalize) -> OldState when
+      OldState :: preliminary | final | volatile;
                         %% These are deliberately not documented
 			(internal_cpu_topology, term()) -> term();
                         (sequential_tracer, pid() | port() | false) -> pid() | port() | false;
@@ -2254,6 +2359,7 @@ tuple_to_list(_Tuple) ->
          (multi_scheduling_blockers) -> [PID :: pid()];
          (nif_version) -> string();
          (otp_release) -> string();
+         (os_monotonic_time_source) -> [{atom(),term()}];
          (port_count) -> non_neg_integer();
          (port_limit) -> pos_integer();
          (process_count) -> pos_integer();
@@ -2271,10 +2377,14 @@ tuple_to_list(_Tuple) ->
          (scheduler_id) -> SchedulerId :: pos_integer();
          (schedulers | schedulers_online) -> pos_integer();
          (smp_support) -> boolean();
+         (start_time) -> integer();
          (system_version) -> string();
          (system_architecture) -> string();
          (threads) -> boolean();
          (thread_pool_size) -> non_neg_integer();
+         (time_correction) -> true | false;
+         (time_offset) -> preliminary | final | volatile;
+         (time_warp_mode) -> no_time_warp | single_time_warp | multi_time_warp;
          (tolerant_timeofday) -> enabled | disabled;
          (trace_control_word) -> non_neg_integer();
          (update_cpu_info) -> changed | unchanged;
@@ -3041,16 +3151,6 @@ integer_to_binary(I0, Base, R0) ->
         true -> integer_to_binary(I1, Base, R1)
     end.
 
-%% erlang:flush_monitor_message/2 is for internal use only!
-%%
-%% erlang:demonitor(Ref, [flush]) traps to
-%% erlang:flush_monitor_message(Ref, Res) when
-%% it needs to flush a monitor message.
-flush_monitor_message(Ref, Res) when erlang:is_reference(Ref),
-                                     erlang:is_atom(Res) ->
-    receive {_, Ref, _, _, _} -> ok after 0 -> ok end,
-    Res.
-
 -record(cpu, {node = -1,
 	      processor = -1,
 	      processor_node = -1,
diff --git a/erts/preloaded/src/erts_internal.erl b/erts/preloaded/src/erts_internal.erl
index 2c5bd82cf0..30df75b406 100644
--- a/erts/preloaded/src/erts_internal.erl
+++ b/erts/preloaded/src/erts_internal.erl
@@ -38,6 +38,10 @@
 
 -export([check_process_code/2]).
 
+-export([flush_monitor_messages/3]).
+
+-export([time_unit/0]).
+
 %%
 %% Await result of send to port
 %%
@@ -178,3 +182,29 @@ cmp_term(_A,_B) ->
 
 map_to_tuple_keys(_M) ->
     erlang:nif_error(undefined).
+
+-spec erts_internal:flush_monitor_messages(Ref, Multi, Res) -> term() when
+      Ref :: reference(),
+      Multi :: boolean(),
+      Res :: term().
+
+%% erlang:demonitor(Ref, [flush]) traps to
+%% erts_internal:flush_monitor_messages(Ref, Res) when
+%% it needs to flush monitor messages.
+flush_monitor_messages(Ref, Multi, Res) when is_reference(Ref) ->
+    receive
+	{_, Ref, _, _, _} ->
+	    case Multi of
+		false ->
+		    Res;
+		_ ->
+		    flush_monitor_messages(Ref, Multi, Res)
+	    end
+    after 0 ->
+	    Res
+    end.
+
+-spec erts_internal:time_unit() -> pos_integer().
+
+time_unit() ->
+    erlang:nif_error(undefined).