Add isc_time_now_hires function to get current time with high resolution

The current isc_time_now uses CLOCK_REALTIME_COARSE which only updates
on a timer tick. This clock is generally fine for millisecond accuracy,
but on servers with 100hz clocks, this clock is nowhere near accurate
enough for microsecond accuracy.

This commit adds a new isc_time_now_hires function that uses
CLOCK_REALTIME, which gives the current time, though it is somewhat
expensive to call. When microsecond accuracy is required, it may be
required to use extra resources for higher accuracy.

lib/isc/include/isc/util.h

@@ -340,6 +340,8 @@ mock_assert(const int result, const char *const expression,
  * Time
  */
 #define TIME_NOW(tp) RUNTIME_CHECK(isc_time_now((tp)) == ISC_R_SUCCESS)
+#define TIME_NOW_HIRES(tp) \
+	RUNTIME_CHECK(isc_time_now_hires((tp)) == ISC_R_SUCCESS)
 
 /*%
  * Alignment

lib/isc/tests/time_test.c

@@ -128,7 +128,7 @@ isc_time_formatISO8601us_test(void **state) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
-	result = isc_time_now(&t);
+	result = isc_time_now_hires(&t);
 	assert_int_equal(result, ISC_R_SUCCESS);
 
 	/* check formatting: yyyy-mm-ddThh:mm:ss.ssssssZ */
@@ -236,7 +236,7 @@ isc_time_formatISO8601Lus_test(void **state) {
 	UNUSED(state);
 
 	setenv("TZ", "America/Los_Angeles", 1);
-	result = isc_time_now(&t);
+	result = isc_time_now_hires(&t);
 	assert_int_equal(result, ISC_R_SUCCESS);
 
 	/* check formatting: yyyy-mm-ddThh:mm:ss.ssssss */

lib/isc/unix/include/isc/time.h

@@ -150,6 +150,26 @@ isc_time_now(isc_time_t *t);
  *		in the current definition of isc_time_t.
  */
 
+isc_result_t
+isc_time_now_hires(isc_time_t *t);
+/*%<
+ * Set 't' to the current absolute time. Uses higher resolution clocks
+ * recommended when microsecond accuracy is required.
+ *
+ * Requires:
+ *
+ *\li	't' is a valid pointer.
+ *
+ * Returns:
+ *
+ *\li	Success
+ *\li	Unexpected error
+ *		Getting the time from the system failed.
+ *\li	Out of range
+ *		The time from the system is too large to be represented
+ *		in the current definition of isc_time_t.
+ */
+
 isc_result_t
 isc_time_nowplusinterval(isc_time_t *t, const isc_interval_t *i);
 /*%<

lib/isc/unix/time.c

@@ -33,6 +33,10 @@
 #define NS_PER_US 1000	     /*%< Nanoseconds per microsecond. */
 #define NS_PER_MS 1000000    /*%< Nanoseconds per millisecond. */
 
+#if defined(CLOCK_REALTIME)
+#define CLOCKSOURCE_HIRES CLOCK_REALTIME
+#endif /* #if defined(CLOCK_REALTIME) */
+
 #if defined(CLOCK_REALTIME_COARSE)
 #define CLOCKSOURCE CLOCK_REALTIME_COARSE
 #elif defined(CLOCK_REALTIME_FAST)
@@ -41,6 +45,10 @@
 #define CLOCKSOURCE CLOCK_REALTIME
 #endif /* if defined(CLOCK_REALTIME_COARSE) */
 
+#if !defined(CLOCKSOURCE_HIRES)
+#define CLOCKSOURCE_HIRES CLOCKSOURCE
+#endif /* #ifndef CLOCKSOURCE_HIRES */
+
 /*%
  *** Intervals
  ***/
@@ -106,14 +114,14 @@ isc_time_isepoch(const isc_time_t *t) {
 	return (false);
 }
 
-isc_result_t
-isc_time_now(isc_time_t *t) {
+static inline isc_result_t
+time_now(isc_time_t *t, clockid_t clock) {
 	struct timespec ts;
 	char strbuf[ISC_STRERRORSIZE];
 
 	REQUIRE(t != NULL);
 
-	if (clock_gettime(CLOCKSOURCE, &ts) == -1) {
+	if (clock_gettime(clock, &ts) == -1) {
 		strerror_r(errno, strbuf, sizeof(strbuf));
 		UNEXPECTED_ERROR(__FILE__, __LINE__, "%s", strbuf);
 		return (ISC_R_UNEXPECTED);
@@ -138,6 +146,16 @@ isc_time_now(isc_time_t *t) {
 	return (ISC_R_SUCCESS);
 }
 
+isc_result_t
+isc_time_now_hires(isc_time_t *t) {
+	return time_now(t, CLOCKSOURCE_HIRES);
+}
+
+isc_result_t
+isc_time_now(isc_time_t *t) {
+	return time_now(t, CLOCKSOURCE);
+}
+
 isc_result_t
 isc_time_nowplusinterval(isc_time_t *t, const isc_interval_t *i) {
 	struct timespec ts;

lib/isc/win32/include/isc/time.h

@@ -164,6 +164,26 @@ isc_time_now(isc_time_t *t);
  *		in the current definition of isc_time_t.
  */
 
+isc_result_t
+isc_time_now_hires(isc_time_t *t);
+/*%<
+ * Set 't' to the current absolute time. Uses higher resolution clocks
+ * recommended when microsecond accuracy is required.
+ *
+ * Requires:
+ *
+ *\li	't' is a valid pointer.
+ *
+ * Returns:
+ *
+ *\li	Success
+ *\li	Unexpected error
+ *		Getting the time from the system failed.
+ *\li	Out of range
+ *		The time from the system is too large to be represented
+ *		in the current definition of isc_time_t.
+ */
+
 isc_result_t
 isc_time_nowplusinterval(isc_time_t *t, const isc_interval_t *i);
 /*

lib/isc/win32/libisc.def.in

@@ -691,6 +691,7 @@ isc_time_isepoch
 isc_time_microdiff
 isc_time_nanoseconds
 isc_time_now
+isc_time_now_hires
 isc_time_nowplusinterval
 isc_time_parsehttptimestamp
 isc_time_secondsastimet

lib/isc/win32/time.c

@@ -124,6 +124,15 @@ isc_time_now(isc_time_t *t) {
 	return (ISC_R_SUCCESS);
 }
 
+isc_result_t
+isc_time_now_hires(isc_time_t *t) {
+	REQUIRE(t != NULL);
+
+	GetSystemTimePreciseAsFileTime(&t->absolute);
+
+	return (ISC_R_SUCCESS);
+}
+
 isc_result_t
 isc_time_nowplusinterval(isc_time_t *t, const isc_interval_t *i) {
 	ULARGE_INTEGER i1;