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, 112 insertions, 17 deletions

diff --git a/erts/emulator/beam/erl_init.c b/erts/emulator/beam/erl_init.c
index 61f8385efc..0e128c9b99 100644
--- a/erts/emulator/beam/erl_init.c
+++ b/erts/emulator/beam/erl_init.c
@@ -45,6 +45,7 @@
 #include "erl_thr_queue.h"
 #include "erl_async.h"
 #include "erl_ptab.h"
+#include "erl_bif_unique.h"
 
 #ifdef HIPE
 #include "hipe_mode_switch.h"	/* for hipe_mode_switch_init() */
@@ -134,7 +135,9 @@ static void erl_init(int ncpu,
 		     int legacy_proc_tab,
 		     int port_tab_sz,
 		     int port_tab_sz_ignore_files,
-		     int legacy_port_tab);
+		     int legacy_port_tab,
+		     int time_correction,
+		     ErtsTimeWarpMode time_warp_mode);
 
 static erts_atomic_t exiting;
 
@@ -188,10 +191,6 @@ static int no_dirty_io_schedulers;
 Uint32 verbose;             /* See erl_debug.h for information about verbose */
 #endif
 
-int erts_disable_tolerant_timeofday; /* Time correction can be disabled it is
-				      * not and/or it is too slow.
-				      */
-
 int erts_atom_table_size = ATOM_LIMIT;	/* Maximum number of atoms */
 
 int erts_modified_timing_level;
@@ -269,6 +268,19 @@ this_rel_num(void)
     return this_rel;
 }
 
+static ERTS_INLINE void
+set_default_time_adj(int *time_correction_p, ErtsTimeWarpMode *time_warp_mode_p)
+{
+    *time_correction_p = 1;
+    *time_warp_mode_p = ERTS_NO_TIME_WARP_MODE;
+    if (!erts_check_time_adj_support(*time_correction_p,
+				     *time_warp_mode_p)) {
+	*time_correction_p = 0;
+	ASSERT(erts_check_time_adj_support(*time_correction_p,
+					   *time_warp_mode_p));
+    }
+}
+
 /*
  * Common error printout function, all error messages
  * that don't go to the error logger go through here.
@@ -284,13 +296,22 @@ static int early_init(int *argc, char **argv);
 void
 erts_short_init(void)
 {
-    int ncpu = early_init(NULL, NULL);
+    
+    int ncpu;
+    int time_correction;
+    ErtsTimeWarpMode time_warp_mode;
+
+    set_default_time_adj(&time_correction,
+			 &time_warp_mode);
+    ncpu = early_init(NULL, NULL);
     erl_init(ncpu,
 	     ERTS_DEFAULT_MAX_PROCESSES,
 	     0,
 	     ERTS_DEFAULT_MAX_PORTS,
 	     0,
-	     0);
+	     0,
+	     time_correction,
+	     time_warp_mode);
     erts_initialized = 1;
 }
 
@@ -300,12 +321,15 @@ erl_init(int ncpu,
 	 int legacy_proc_tab,
 	 int port_tab_sz,
 	 int port_tab_sz_ignore_files,
-	 int legacy_port_tab)
+	 int legacy_port_tab,
+	 int time_correction,
+	 ErtsTimeWarpMode time_warp_mode)
 {
     init_benchmarking();
 
+    erts_bif_unique_init();
     erts_init_monitors();
-    erts_init_time();
+    erts_init_time(time_correction, time_warp_mode);
     erts_init_sys_common_misc();
     erts_init_process(ncpu, proc_tab_sz, legacy_proc_tab);
     erts_init_scheduling(no_schedulers,
@@ -509,9 +533,9 @@ void erts_usage(void)
 
     /*    erts_fprintf(stderr, "-b func    set the boot function (default boot)\n"); */
 
-    erts_fprintf(stderr, "-c             disable continuous date/time correction with\n");
-    erts_fprintf(stderr, "               respect to uptime\n");
-
+    erts_fprintf(stderr, "-c bool        enable or disable time correction\n");
+    erts_fprintf(stderr, "-C mode        set time warp mode; valid modes are:\n");
+    erts_fprintf(stderr, "               no_time_warp|single_time_warp|multi_time_warp\n");
     erts_fprintf(stderr, "-d             don't write a crash dump for internally detected errors\n");
     erts_fprintf(stderr, "               (halt(String) will still produce a crash dump)\n");
     erts_fprintf(stderr, "-fn[u|a|l]     Control how filenames are interpreted\n");
@@ -681,7 +705,6 @@ early_init(int *argc, char **argv) /*
 
     erts_sched_compact_load = 1;
     erts_printf_eterm_func = erts_printf_term;
-    erts_disable_tolerant_timeofday = 0;
     display_items = 200;
     erts_backtrace_depth = DEFAULT_BACKTRACE_SIZE;
     erts_async_max_threads = ERTS_DEFAULT_NO_ASYNC_THREADS;
@@ -1144,6 +1167,7 @@ early_init(int *argc, char **argv) /*
 
     /* Creates threads on Windows that depend on the arguments, so has to be after erl_sys_args */
     erl_sys_init();
+    erts_early_init_time_sup();
 
     erts_ets_realloc_always_moves = 0;
     erts_ets_always_compress = 0;
@@ -1187,7 +1211,11 @@ erl_start(int argc, char **argv)
     int port_tab_sz_ignore_files = 0;
     int legacy_proc_tab = 0;
     int legacy_port_tab = 0;
+    int time_correction;
+    ErtsTimeWarpMode time_warp_mode;
 
+    set_default_time_adj(&time_correction,
+			 &time_warp_mode);
 
     envbufsz = sizeof(envbuf);
     if (erts_sys_getenv_raw(ERL_MAX_ETS_TABLES_ENV, envbuf, &envbufsz) == 0)
@@ -1896,15 +1924,56 @@ erl_start(int argc, char **argv)
 	    }
 	    break;
 	}
-	case 'c':
-	    if (argv[i][2] == 0) { /* -c: documented option */
-		erts_disable_tolerant_timeofday = 1;
+	case 'C':
+	    arg = get_arg(argv[i]+2, argv[i+1], &i);
+	    if (sys_strcmp(arg, "no_time_warp") == 0)
+		time_warp_mode = ERTS_NO_TIME_WARP_MODE;
+	    else if (sys_strcmp(arg, "single_time_warp") == 0)
+		time_warp_mode = ERTS_SINGLE_TIME_WARP_MODE;
+	    else if (sys_strcmp(arg, "multi_time_warp") == 0)
+		time_warp_mode = ERTS_MULTI_TIME_WARP_MODE;
+	    else {
+		erts_fprintf(stderr,
+			     "Invalid time warp mode: %s\n", arg);
+		erts_usage();
 	    }
+	    break;
+	case 'c':
+	    if (sys_strcmp(argv[i]+2, "false") == 0)
+		goto time_correction_false;
+	    else if (sys_strcmp(argv[i]+2, "true") == 0)
+		goto time_correction_true;
 #ifdef ERTS_OPCODE_COUNTER_SUPPORT
 	    else if (argv[i][2] == 'i') { /* -ci: undcoumented option*/
 		count_instructions = 1;
 	    }
 #endif
+	    else if (argv[i][2] == '\0') {
+		if (i + 1 >= argc)
+		    goto time_correction_false;
+		else {
+		    if (sys_strcmp(argv[i+1], "false") == 0) {
+			(void) get_arg(argv[i]+2, argv[i+1], &i);
+			goto time_correction_false;
+		    }
+		    else if (sys_strcmp(argv[i+1], "true") == 0) {
+			(void) get_arg(argv[i]+2, argv[i+1], &i);
+		    time_correction_true:
+			time_correction = 1;
+			break;
+		    }
+		    else {
+		    time_correction_false:
+			time_correction = 0;
+			break;
+		    }
+		}
+	    }
+	    else {
+		arg = get_arg(argv[i]+2, argv[i+1], &i);
+		erts_fprintf(stderr, "Invalid time correnction value: %s\n", arg);
+		erts_usage();
+	    }
 	    break;
 	case 'W':
 	    arg = get_arg(argv[i]+2, argv[i+1], &i);
@@ -1950,6 +2019,30 @@ erl_start(int argc, char **argv)
 	i++;
     }
 
+    if (!erts_check_time_adj_support(time_correction, time_warp_mode)) {
+	char *time_correction_str = time_correction ? "Enabled" : "Disabled";
+	char *time_warp_str = "undefined";
+	switch (time_warp_mode) {
+	case ERTS_NO_TIME_WARP_MODE:
+	    time_warp_str = "no";
+	    break;
+	case ERTS_SINGLE_TIME_WARP_MODE:
+	    time_warp_str = "single";
+	    break;
+	case ERTS_MULTI_TIME_WARP_MODE:
+	    time_warp_str = "multi";
+	    break;
+	default:
+	    time_warp_str = "undefined";
+	    break;
+	}
+	erts_fprintf(stderr, "%s time correction with %s time warp mode "
+		     "is not supported on this platform\n",
+		     time_correction_str,
+		     time_warp_str);
+	erts_usage();
+    }
+
 /* Output format on windows for sprintf defaults to three exponents.
  * We use two-exponent to mimic normal sprintf behaviour.
  */
@@ -1983,7 +2076,9 @@ erl_start(int argc, char **argv)
 	     legacy_proc_tab,
 	     port_tab_sz,
 	     port_tab_sz_ignore_files,
-	     legacy_port_tab);
+	     legacy_port_tab,
+	     time_correction,
+	     time_warp_mode);
 
     load_preloaded();
     erts_end_staging_code_ix();