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, 124 insertions, 153 deletions

diff --git a/erts/emulator/beam/bif.c b/erts/emulator/beam/bif.c
index 42dd160e38..ec5122292e 100644
--- a/erts/emulator/beam/bif.c
+++ b/erts/emulator/beam/bif.c
@@ -40,16 +40,21 @@
 #define ERTS_PTAB_WANT_BIF_IMPL__
 #include "erl_ptab.h"
 #include "erl_bits.h"
+#include "erl_bif_unique.h"
 
-static Export* flush_monitor_message_trap = NULL;
+static Export* flush_monitor_messages_trap = NULL;
 static Export* set_cpu_topology_trap = NULL;
 static Export* await_proc_exit_trap = NULL;
 static Export* await_port_send_result_trap = NULL;
 Export* erts_format_cpu_topology_trap = NULL;
+Export *erts_convert_time_unit_trap = NULL;
 
 static Export *await_sched_wall_time_mod_trap;
 static erts_smp_atomic32_t sched_wall_time;
 
+static erts_smp_mtx_t ports_snapshot_mtx;
+erts_smp_atomic_t erts_dead_ports_ptr; /* To store dying ports during snapshot */
+
 #define DECL_AM(S) Eterm AM_ ## S = am_atom_put(#S, sizeof(#S) - 1)
 
 /*
@@ -391,7 +396,7 @@ remote_demonitor(Process *c_p, DistEntry *dep, Eterm ref, Eterm to)
     return res;
 }
 
-static int demonitor(Process *c_p, Eterm ref)
+static int demonitor(Process *c_p, Eterm ref, Eterm *multip)
 {
    ErtsMonitor *mon = NULL;  /* The monitor entry to delete */
    Process  *rp;    /* Local target process */
@@ -415,65 +420,73 @@ static int demonitor(Process *c_p, Eterm ref)
        goto done;
    }
 
-   if (mon->type != MON_ORIGIN) {
-       res = ERTS_DEMONITOR_BADARG;
-       goto done;
-   }
-   to = mon->pid;
-
-   if (is_atom(to)) {
-       /* Monitoring a name at node to */
-       ASSERT(is_node_name_atom(to));
-       dep = erts_sysname_to_connected_dist_entry(to);
-       ASSERT(dep != erts_this_dist_entry);
-       if (dep)
-	   deref_de = 1;
-   } else {
-       ASSERT(is_pid(to));
-       dep = pid_dist_entry(to);
-   }
-   if (dep != erts_this_dist_entry) {
-       res = remote_demonitor(c_p, dep, ref, to);
-       /* remote_demonitor() unlocks link lock on c_p */
-       unlock_link = 0;
-   }
-   else { /* Local monitor */
-       if (deref_de) {
-	   deref_de = 0;
-	   erts_deref_dist_entry(dep);
+   switch (mon->type) {
+   case MON_TIME_OFFSET:
+       *multip = am_true;
+       erts_demonitor_time_offset(ref);
+       res = ERTS_DEMONITOR_TRUE;
+       break;
+   case MON_ORIGIN:
+       to = mon->pid;
+       *multip = am_false;
+       if (is_atom(to)) {
+	   /* Monitoring a name at node to */
+	   ASSERT(is_node_name_atom(to));
+	   dep = erts_sysname_to_connected_dist_entry(to);
+	   ASSERT(dep != erts_this_dist_entry);
+	   if (dep)
+	       deref_de = 1;
+       } else {
+	   ASSERT(is_pid(to));
+	   dep = pid_dist_entry(to);
        }
-       dep = NULL;
-       rp = erts_pid2proc_opt(c_p,
-			      ERTS_PROC_LOCK_MAIN|ERTS_PROC_LOCK_LINK,
-			      to,
-			      ERTS_PROC_LOCK_LINK,
-			      ERTS_P2P_FLG_ALLOW_OTHER_X);
-       mon = erts_remove_monitor(&ERTS_P_MONITORS(c_p), ref);
+       if (dep != erts_this_dist_entry) {
+	   res = remote_demonitor(c_p, dep, ref, to);
+	   /* remote_demonitor() unlocks link lock on c_p */
+	   unlock_link = 0;
+       }
+       else { /* Local monitor */
+	   if (deref_de) {
+	       deref_de = 0;
+	       erts_deref_dist_entry(dep);
+	   }
+	   dep = NULL;
+	   rp = erts_pid2proc_opt(c_p,
+				  ERTS_PROC_LOCK_MAIN|ERTS_PROC_LOCK_LINK,
+				  to,
+				  ERTS_PROC_LOCK_LINK,
+				  ERTS_P2P_FLG_ALLOW_OTHER_X);
+	   mon = erts_remove_monitor(&ERTS_P_MONITORS(c_p), ref);
 #ifndef ERTS_SMP
-       ASSERT(mon);
+	   ASSERT(mon);
 #else
-       if (!mon)
-	   res = ERTS_DEMONITOR_FALSE;
-       else
+	   if (!mon)
+	       res = ERTS_DEMONITOR_FALSE;
+	   else
 #endif
-       {
-	   res = ERTS_DEMONITOR_TRUE;
-	   erts_destroy_monitor(mon);
-       }
-       if (rp) {
-	   ErtsMonitor *rmon;
-	   rmon = erts_remove_monitor(&ERTS_P_MONITORS(rp), ref);
-	   if (rp != c_p)
-	       erts_smp_proc_unlock(rp, ERTS_PROC_LOCK_LINK);
-	   if (rmon != NULL)
-	       erts_destroy_monitor(rmon);
-       }
-       else {
-	   ERTS_SMP_ASSERT_IS_NOT_EXITING(c_p);
-       }
+	   {
+	       res = ERTS_DEMONITOR_TRUE;
+	       erts_destroy_monitor(mon);
+	   }
+	   if (rp) {
+	       ErtsMonitor *rmon;
+	       rmon = erts_remove_monitor(&ERTS_P_MONITORS(rp), ref);
+	       if (rp != c_p)
+		   erts_smp_proc_unlock(rp, ERTS_PROC_LOCK_LINK);
+	       if (rmon != NULL)
+		   erts_destroy_monitor(rmon);
+	   }
+	   else {
+	       ERTS_SMP_ASSERT_IS_NOT_EXITING(c_p);
+	   }
 
+       }
+       break;
+   default:
+       res = ERTS_DEMONITOR_BADARG;
+       *multip = am_false;
+       break;
    }
-
  done:
 
    if (unlock_link)
@@ -490,7 +503,8 @@ static int demonitor(Process *c_p, Eterm ref)
 
 BIF_RETTYPE demonitor_1(BIF_ALIST_1)
 {
-    switch (demonitor(BIF_P, BIF_ARG_1)) {
+    Eterm multi;
+    switch (demonitor(BIF_P, BIF_ARG_1, &multi)) {
     case ERTS_DEMONITOR_FALSE:
     case ERTS_DEMONITOR_TRUE:
 	BIF_RET(am_true);
@@ -508,6 +522,7 @@ BIF_RETTYPE demonitor_1(BIF_ALIST_1)
 BIF_RETTYPE demonitor_2(BIF_ALIST_2)
 {
     Eterm res = am_true;
+    Eterm multi = am_false;
     int info = 0;
     int flush = 0;
     Eterm list = BIF_ARG_2;
@@ -530,13 +545,18 @@ BIF_RETTYPE demonitor_2(BIF_ALIST_2)
     if (is_not_nil(list))
 	goto badarg;
 
-    switch (demonitor(BIF_P, BIF_ARG_1)) {
+    switch (demonitor(BIF_P, BIF_ARG_1, &multi)) {
     case ERTS_DEMONITOR_FALSE:
 	if (info)
 	    res = am_false;
-	if (flush)
-	    BIF_TRAP2(flush_monitor_message_trap, BIF_P, BIF_ARG_1, res);
+	if (flush) {
+	flush_messages:
+	    BIF_TRAP3(flush_monitor_messages_trap, BIF_P,
+		      BIF_ARG_1, multi, res);
+	}
     case ERTS_DEMONITOR_TRUE:
+	if (multi == am_true && flush)
+	    goto flush_messages;
 	BIF_RET(res);
     case ERTS_DEMONITOR_YIELD_TRUE:
 	ERTS_BIF_YIELD_RETURN(BIF_P, am_true);
@@ -744,7 +764,22 @@ BIF_RETTYPE monitor_2(BIF_ALIST_2)
     int deref_de = 0;
 
     /* Only process monitors are implemented */
-    if (BIF_ARG_1 != am_process) {
+    switch (BIF_ARG_1) {
+    case am_time_offset: {
+	Eterm ref;
+	if (BIF_ARG_2 != am_clock_service)
+	    goto error;
+	ref = erts_make_ref(BIF_P);
+	erts_smp_proc_lock(BIF_P, ERTS_PROC_LOCK_LINK);
+	erts_add_monitor(&ERTS_P_MONITORS(BIF_P), MON_TIME_OFFSET,
+			 ref, am_clock_service, NIL);
+	erts_smp_proc_unlock(BIF_P, ERTS_PROC_LOCK_LINK);
+	erts_monitor_time_offset(BIF_P->common.id, ref);
+	BIF_RET(ref);
+    }
+    case am_process:
+	break;
+    default:
 	goto error;
     }
 
@@ -3446,91 +3481,6 @@ BIF_RETTYPE self_0(BIF_ALIST_0)
 
 /**********************************************************************/
 
-/*
-   New representation of refs in R9, see erl_term.h
-
-   In the first data word, only the usual 18 bits are used. Ordinarily,
-   in "long refs" all words are used (in other words, practically never
-   wrap around), but for compatibility with older nodes, "short refs"
-   exist. Short refs come into being by being converted from the old
-   external format for refs (tag REFERENCE_EXT). Short refs are
-   converted back to the old external format.
-
-   When converting a long ref to the external format in the case of
-   preparing for sending to an older node, the ref is truncated by only
-   using the first word (with 18 significant bits), and using the old tag
-   REFERENCE_EXT.
-
-   When comparing refs or different size, only the parts up to the length
-   of the shorter operand are used. This has the desirable effect that a
-   long ref sent to an old node and back will be treated as equal to
-   the original, although some of the bits have been lost.
-
-   The hash value for a ref always considers only the first word, since
-   in the above scenario, the original and the copy should have the same
-   hash value.
-*/
-
-static Uint32 reference0; /* Initialized in erts_init_bif */
-static Uint32 reference1;
-static Uint32 reference2;
-static erts_smp_spinlock_t make_ref_lock;
-static erts_smp_mtx_t ports_snapshot_mtx;
-erts_smp_atomic_t erts_dead_ports_ptr; /* To store dying ports during snapshot */
-
-void
-erts_make_ref_in_array(Uint32 ref[ERTS_MAX_REF_NUMBERS])
-{
-    erts_smp_spin_lock(&make_ref_lock);
-
-    reference0++;
-    if (reference0 >= MAX_REFERENCE) {
-	reference0 = 0;
-	reference1++;
-	if (reference1 == 0) {
-	    reference2++;
-	}
-    }
-
-    ref[0] = reference0;
-    ref[1] = reference1;
-    ref[2] = reference2;
-
-    erts_smp_spin_unlock(&make_ref_lock);
-}
-
-Eterm erts_make_ref_in_buffer(Eterm buffer[REF_THING_SIZE])
-{
-    Eterm* hp = buffer;
-    Uint32 ref[ERTS_MAX_REF_NUMBERS];
-
-    erts_make_ref_in_array(ref);
-    write_ref_thing(hp, ref[0], ref[1], ref[2]);
-    return make_internal_ref(hp);
-}
-
-Eterm erts_make_ref(Process *p)
-{
-    Eterm* hp;
-    Uint32 ref[ERTS_MAX_REF_NUMBERS];
-
-    ERTS_SMP_LC_ASSERT(ERTS_PROC_LOCK_MAIN & erts_proc_lc_my_proc_locks(p));
-
-    hp = HAlloc(p, REF_THING_SIZE);
-
-    erts_make_ref_in_array(ref);
-    write_ref_thing(hp, ref[0], ref[1], ref[2]);
-
-    return make_internal_ref(hp);
-}
-
-BIF_RETTYPE make_ref_0(BIF_ALIST_0)
-{
-    return erts_make_ref(BIF_P);
-}
-
-/**********************************************************************/
-
 /* return the time of day */
 
 BIF_RETTYPE time_0(BIF_ALIST_0)
@@ -4508,6 +4458,28 @@ BIF_RETTYPE system_flag_2(BIF_ALIST_2)
 	    break;
 	}
 #endif
+    } else if (BIF_ARG_1 == am_time_offset
+	       && ERTS_IS_ATOM_STR("finalize", BIF_ARG_2)) {
+	ErtsTimeOffsetState res;
+	erts_smp_proc_unlock(BIF_P, ERTS_PROC_LOCK_MAIN);
+	res = erts_finalize_time_offset();
+        erts_smp_proc_lock(BIF_P, ERTS_PROC_LOCK_MAIN);
+	switch (res) {
+	case ERTS_TIME_OFFSET_PRELIMINARY: {
+	    DECL_AM(preliminary);
+	    BIF_RET(AM_preliminary);
+	}
+	case ERTS_TIME_OFFSET_FINAL: {
+	    DECL_AM(final);
+	    BIF_RET(AM_final);
+	}
+	case ERTS_TIME_OFFSET_VOLATILE: {
+	    DECL_AM(volatile);
+	    BIF_RET(AM_volatile);
+	}
+	default:
+	    ERTS_INTERNAL_ERROR("Unknown state");
+	}
     } else if (ERTS_IS_ATOM_STR("scheduling_statistics", BIF_ARG_1)) {
 	int what;
 	if (ERTS_IS_ATOM_STR("disable", BIF_ARG_2))
@@ -4795,11 +4767,6 @@ void erts_init_trap_export(Export* ep, Eterm m, Eterm f, Uint a,
 
 void erts_init_bif(void)
 {
-    reference0 = 0;
-    reference1 = 0;
-    reference2 = 0;
-
-    erts_smp_spinlock_init(&make_ref_lock, "make_ref");
     erts_smp_mtx_init(&ports_snapshot_mtx, "ports_snapshot");
     erts_smp_atomic_init_nob(&erts_dead_ports_ptr, (erts_aint_t) NULL);
 
@@ -4816,9 +4783,13 @@ void erts_init_bif(void)
 #endif
 		     , &bif_return_trap);
 
-    flush_monitor_message_trap = erts_export_put(am_erlang,
-						 am_flush_monitor_message,
-						 2);
+    flush_monitor_messages_trap = erts_export_put(am_erts_internal,
+						  am_flush_monitor_messages,
+						  3);
+
+    erts_convert_time_unit_trap = erts_export_put(am_erlang,
+						  am_convert_time_unit,
+						  3);
 
     set_cpu_topology_trap = erts_export_put(am_erlang,
 					    am_set_cpu_topology,