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.

1 files changed, 65 insertions, 31 deletions

diff --git a/erts/emulator/test/long_timers_test.erl b/erts/emulator/test/long_timers_test.erl
index 28a4fba9f6..f381332b51 100644
--- a/erts/emulator/test/long_timers_test.erl
+++ b/erts/emulator/test/long_timers_test.erl
@@ -28,7 +28,7 @@
 
 
 -define(MAX_TIMEOUT, 60). % Minutes
--define(MAX_LATE, 10*1000). % Milliseconds
+-define(MAX_LATE_MS, 10*1000). % Milliseconds
 -define(REG_NAME, '___LONG___TIMERS___TEST___SERVER___').
 
 -define(DRV_NAME, timer_driver).
@@ -75,7 +75,7 @@ check_result() ->
 	    erlang:demonitor(Mon),
 	    receive {'DOWN', Mon, _, _, _} -> ok after 0 -> ok end,
 	    stop_node(Node),
-	    check(TORs, (timer:now_diff(End, Start) div 1000) - ?MAX_LATE, ok)
+	    check(TORs, ms((End - Start) - max_late()), ok)
     end.
 
 check([#timeout_rec{timeout = Timeout,
@@ -83,7 +83,7 @@ check([#timeout_rec{timeout = Timeout,
 		    timeout_diff = undefined} | TORs],
       NeedRes,
       _Ok) when Timeout < NeedRes ->
-    io:format("~p timeout = ~p failed! No timeout.~n",
+    io:format("~p timeout = ~p ms failed! No timeout.~n",
 	      [Type, Timeout]),
     check(TORs, NeedRes, failed);
 check([#timeout_rec{timeout_diff = undefined} | TORs],
@@ -95,7 +95,7 @@ check([#timeout_rec{timeout = Timeout,
 		    timeout_diff = {error, Reason}} | TORs],
       NeedRes,
       _Ok) ->
-    io:format("~p timeout = ~p failed! exit reason ~p~n",
+    io:format("~p timeout = ~p ms failed! exit reason ~p~n",
 	      [Type, Timeout, Reason]),
     check(TORs, NeedRes, failed);
 check([#timeout_rec{timeout = Timeout,
@@ -103,43 +103,77 @@ check([#timeout_rec{timeout = Timeout,
 		    timeout_diff = TimeoutDiff} | TORs],
       NeedRes,
       Ok) ->
-    case (0 =< TimeoutDiff) and (TimeoutDiff =< ?MAX_LATE) of
-	true ->
-	    io:format("~p timeout = ~p succeded! timeout diff = ~p.~n",
-		      [Type, Timeout, TimeoutDiff]),
-	    check(TORs, NeedRes, Ok);
-	false ->
-	    io:format("~p timeout = ~p failed! timeout diff = ~p.~n",
-		      [Type, Timeout, TimeoutDiff]),
-	    check(TORs, NeedRes, failed)
-    end;
+    {NewOk, SuccessStr} = case ((0 =< TimeoutDiff)
+				andalso (TimeoutDiff =< max_late())) of
+			      true -> {Ok, "succeeded"};
+			      false -> {failed, "FAILED"}
+			  end,
+    io:format("~s timeout = ~s ms ~s! timeout diff = ~s.~n",
+	      [type_str(Type),
+	       time_str(Timeout),
+	       SuccessStr,
+	       time_str(TimeoutDiff, erlang:convert_time_unit(1, seconds, native))]),
+    check(TORs, NeedRes, NewOk);
 check([], _NeedRes, Ok) ->
     Ok.
 
+type_str(receive_after) -> "receive ... after";
+type_str(bif_timer) -> "BIF timer";
+type_str(driver) -> "driver".
+
+time_str(Time, Unit) ->
+    lists:flatten([time_str(Time), " ", unit_str(Unit)]).
+
+time_str(Time) ->
+    lists:reverse(conv_time_str(lists:reverse(integer_to_list(Time)))).
+
+conv_time_str([X,Y,Z,C|Cs]) when C /= $- ->
+    [X,Y,Z,$`|conv_time_str([C|Cs])];
+conv_time_str(Cs) ->
+    Cs.
+
+unit_str(1) -> "s";
+unit_str(1000) -> "ms";
+unit_str(1000000) -> "us";
+unit_str(1000000000) -> "ns";
+unit_str(Res) when is_integer(Res) -> ["/ ", integer_to_list(Res), " s"];
+unit_str(Res) -> Res.
+
+to_diff(Timeout, Start, Stop) ->
+    %% 'Timeout' in milli seconds
+    %% 'Start', 'Stop', and result in native unit
+    (Stop - Start) - erlang:convert_time_unit(Timeout, milli_seconds, native).
+
+ms(Time) ->
+    erlang:convert_time_unit(Time, native, milli_seconds).
+
+max_late() ->
+    erlang:convert_time_unit(?MAX_LATE_MS, milli_seconds, native).
+
 receive_after(Timeout) ->
-    Start = now(),
+    Start = erlang:monotonic_time(),
     receive
 	{get_result, ?REG_NAME} ->
 	    ?REG_NAME ! #timeout_rec{pid = self(),
 				     type = receive_after,
 				     timeout = Timeout}
     after Timeout ->
-	    Stop = now(),
+	    Stop = erlang:monotonic_time(),
 	    receive
 		{get_result, ?REG_NAME} ->
-	    	    TimeoutDiff = ((timer:now_diff(Stop, Start) div 1000)
-				   - Timeout),
 		    ?REG_NAME ! #timeout_rec{pid = self(),
 					     type = receive_after,
 					     timeout = Timeout,
-					     timeout_diff = TimeoutDiff}
+					     timeout_diff = to_diff(Timeout,
+								    Start,
+								    Stop)}
 	    end
     end.
 
 driver(Timeout) ->
     Port = open_port({spawn, ?DRV_NAME},[]),
     link(Port),
-    Start = now(),
+    Start = erlang:monotonic_time(),
     erlang:port_command(Port, <<?START_TIMER, Timeout:32>>),
     receive
 	{get_result, ?REG_NAME} ->
@@ -147,38 +181,38 @@ driver(Timeout) ->
 				     type = driver,
 				     timeout = Timeout};
 	{Port,{data,[?TIMER]}} ->
-	    Stop = now(),
+	    Stop = erlang:monotonic_time(),
 	    unlink(Port),
 	    true = erlang:port_close(Port),
 	    receive
 		{get_result, ?REG_NAME} ->
-	    	    TimeoutDiff = ((timer:now_diff(Stop, Start) div 1000)
-				   - Timeout),
 		    ?REG_NAME ! #timeout_rec{pid = self(),
 					     type = driver,
 					     timeout = Timeout,
-					     timeout_diff = TimeoutDiff}
+					     timeout_diff = to_diff(Timeout,
+								    Start,
+								    Stop)}
 	    end
     end.
 
 bif_timer(Timeout) ->
     Tmr = erlang:start_timer(Timeout, self(), ok),
-    Start = now(),
+    Start = erlang:monotonic_time(),
     receive
 	{get_result, ?REG_NAME} ->
 	    ?REG_NAME ! #timeout_rec{pid = self(),
 				     type = bif_timer,
 				     timeout = Timeout};
 	{timeout, Tmr, ok} ->
-	    Stop = now(),
+	    Stop = erlang:monotonic_time(),
 	    receive
 		{get_result, ?REG_NAME} ->
-	    	    TimeoutDiff = ((timer:now_diff(Stop, Start) div 1000)
-				   - Timeout),
 		    ?REG_NAME ! #timeout_rec{pid = self(),
 					     type = bif_timer,
 					     timeout = Timeout,
-					     timeout_diff = TimeoutDiff}
+					     timeout_diff = to_diff(Timeout,
+								    Start,
+								    Stop)}
 	    end
     end.
 
@@ -189,7 +223,7 @@ test(Starter, DrvDir, StartDone) ->
     register(?REG_NAME, self()),
     {group_leader, GL} = process_info(whereis(net_kernel),group_leader),
     group_leader(GL, self()),
-    Start = now(),
+    Start = erlang:monotonic_time(),
     TORs = lists:map(fun (Min) ->
 			     TO = Min*60*1000,
 			     [#timeout_rec{pid = spawn_opt(
@@ -222,7 +256,7 @@ test(Starter, DrvDir, StartDone) ->
 test_loop(TORs, Start) ->
     receive
 	{get_result, ?REG_NAME, Pid} ->
-	    End = now(),
+	    End = erlang:monotonic_time(),
 	    Pid ! {result, ?REG_NAME, get_test_results(TORs), Start, End},
 	    erl_ddll:unload_driver(?DRV_NAME),
 	    erl_ddll:stop(),