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authorRickard Green <rickard@erlang.org>2011-12-16 13:02:09 +0100
committerRickard Green <rickard@erlang.org>2012-04-16 16:32:28 +0200
commit414f4fb8dc9a188f8148a1f92e5f9125108e170d (patch)
tree319b52ff0171a0f3bec1deb63407caaefe095ab5 /erts/emulator/beam/erl_time_sup.c
parent3e454414a40bba082e5dc0be310f71843200dcf4 (diff)
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Optimize process table access
Diffstat (limited to 'erts/emulator/beam/erl_time_sup.c')
-rw-r--r--erts/emulator/beam/erl_time_sup.c85
1 files changed, 48 insertions, 37 deletions
diff --git a/erts/emulator/beam/erl_time_sup.c b/erts/emulator/beam/erl_time_sup.c
index 1d0735aa99..c1b4408c06 100644
--- a/erts/emulator/beam/erl_time_sup.c
+++ b/erts/emulator/beam/erl_time_sup.c
@@ -91,6 +91,41 @@ static SysTimeval then; /* Used in get_now */
static SysTimeval last_emu_time; /* Used in erts_get_emu_time() */
SysTimeval erts_first_emu_time; /* Used in erts_get_emu_time() */
+union {
+ erts_smp_atomic_t time;
+ char align[ERTS_CACHE_LINE_SIZE];
+} approx erts_align_attribute(ERTS_CACHE_LINE_SIZE);
+
+static void
+init_approx_time(void)
+{
+ erts_smp_atomic_init_nob(&approx.time, 0);
+}
+
+static ERTS_INLINE erts_approx_time_t
+get_approx_time(void)
+{
+ return (erts_approx_time_t) erts_smp_atomic_read_nob(&approx.time);
+}
+
+static ERTS_INLINE void
+update_approx_time(SysTimeval *tv)
+{
+ erts_approx_time_t new_secs = (erts_approx_time_t) tv->tv_sec;
+ erts_approx_time_t old_secs = get_approx_time();
+ if (old_secs != new_secs)
+ erts_smp_atomic_set_nob(&approx.time, new_secs);
+}
+
+/*
+ * erts_get_approx_time() returns an *approximate* time
+ * in seconds. NOTE that this time may jump backwards!!!
+ */
+erts_approx_time_t
+erts_get_approx_time(void)
+{
+ return get_approx_time();
+}
#ifdef HAVE_GETHRTIME
@@ -398,6 +433,8 @@ erts_init_time_sup(void)
{
erts_smp_mtx_init(&erts_timeofday_mtx, "timeofday");
+ init_approx_time();
+
last_emu_time.tv_sec = 0;
last_emu_time.tv_usec = 0;
@@ -417,7 +454,7 @@ erts_init_time_sup(void)
gtv = inittv;
then.tv_sec = then.tv_usec = 0;
- erts_get_emu_time(&erts_first_emu_time);
+ erts_deliver_time();
return CLOCK_RESOLUTION;
}
@@ -873,6 +910,8 @@ get_now(Uint* megasec, Uint* sec, Uint* microsec)
*megasec = (Uint) (now.tv_sec / 1000000);
*sec = (Uint) (now.tv_sec % 1000000);
*microsec = (Uint) (now.tv_usec);
+
+ update_approx_time(&now);
}
void
@@ -885,6 +924,8 @@ get_sys_now(Uint* megasec, Uint* sec, Uint* microsec)
*megasec = (Uint) (now.tv_sec / 1000000);
*sec = (Uint) (now.tv_sec % 1000000);
*microsec = (Uint) (now.tv_usec);
+
+ update_approx_time(&now);
}
@@ -901,6 +942,8 @@ void erts_deliver_time(void) {
do_erts_deliver_time(&now);
erts_smp_mtx_unlock(&erts_timeofday_mtx);
+
+ update_approx_time(&now);
}
/* get *real* time (not ticks) remaining until next timeout - if there
@@ -949,6 +992,7 @@ void erts_get_timeval(SysTimeval *tv)
erts_smp_mtx_lock(&erts_timeofday_mtx);
get_tolerant_timeofday(tv);
erts_smp_mtx_unlock(&erts_timeofday_mtx);
+ update_approx_time(tv);
}
erts_time_t
@@ -961,7 +1005,9 @@ erts_get_time(void)
get_tolerant_timeofday(&sys_tv);
erts_smp_mtx_unlock(&erts_timeofday_mtx);
-
+
+ update_approx_time(&sys_tv);
+
return sys_tv.tv_sec;
}
@@ -977,38 +1023,3 @@ void erts_get_now_cpu(Uint* megasec, Uint* sec, Uint* microsec) {
*sec = (Uint)(tp.tv_sec % 1000000);
}
#endif
-
-
-/*
- * erts_get_emu_time() is similar to get_now(). You will
- * always get different times from erts_get_emu_time(), but they
- * may equal a time from get_now().
- *
- * erts_get_emu_time() is only used internally in the emulator in
- * order to order emulator internal events.
- */
-
-void
-erts_get_emu_time(SysTimeval *this_emu_time_p)
-{
- erts_smp_mtx_lock(&erts_timeofday_mtx);
-
- get_tolerant_timeofday(this_emu_time_p);
-
- /* Make sure time is later than last */
- if (last_emu_time.tv_sec > this_emu_time_p->tv_sec ||
- (last_emu_time.tv_sec == this_emu_time_p->tv_sec
- && last_emu_time.tv_usec >= this_emu_time_p->tv_usec)) {
- *this_emu_time_p = last_emu_time;
- this_emu_time_p->tv_usec++;
- }
- /* Check for carry from above + general reasonability */
- if (this_emu_time_p->tv_usec >= 1000000) {
- this_emu_time_p->tv_usec = 0;
- this_emu_time_p->tv_sec++;
- }
-
- last_emu_time = *this_emu_time_p;
-
- erts_smp_mtx_unlock(&erts_timeofday_mtx);
-}