time: Make ceph_time clocks work under BSD

Linux's naming things _COARSE is non-standard. Other systems name them other
things.

BSD also names its precise clocks _PRECISE and defines the unmarked versions to
_FAST, so make sure we use _PRECISE when we want a high-resolution timer.

Signed-off-by: Adam C. Emerson <aemerson@redhat.com>

src/common/ceph_time.h

@@ -68,7 +68,14 @@ namespace ceph {
 
       static time_point now() noexcept {
 	struct timespec ts;
+#if defined(CLOCK_REALTIME_PRECISE)
+	// FreeBSD defines CLOCK_REALTIME to CLOCK_REALTIME_FAST. This
+	// way we'll have high-resolution for real_clock on both
+	// BSD and Linux.
+	clock_gettime(CLOCK_REALTIME_PRECISE, &ts);
+#else
 	clock_gettime(CLOCK_REALTIME, &ts);
+#endif
 	return from_timespec(ts);
       }
       // We need a version of 'now' that can take a CephContext for
@@ -151,7 +158,18 @@ namespace ceph {
 
       static time_point now() noexcept {
 	struct timespec ts;
+#if defined(CLOCK_REALTIME_COARSE)
+	// Linux systems have _COARSE clocks.
 	clock_gettime(CLOCK_REALTIME_COARSE, &ts);
+#elif defined(CLOCK_REALTIME_FAST)
+	// BSD systems have _FAST clocks.
+	clock_gettime(CLOCK_REALTIME_FAST, &ts);
+#else
+	// And if we find neither, you may wish to consult your system's
+	// documentation.
+#warning Falling back to CLOCK_REALTIME, may be slow.
+	clock_gettime(CLOCK_REALTIME, &ts);
+#endif
 	return from_timespec(ts);
       }
       static time_point now(const CephContext* cct) noexcept;
@@ -214,7 +232,14 @@ namespace ceph {
 
       static time_point now() noexcept {
 	struct timespec ts;
+#if defined(CLOCK_MONOTONIC_PRECISE)
+	// FreeBSD defines CLOCK_MONOTONIC to CLOCK_MONOTONIC_FAST. This
+	// way we'll have high-resolution for mono_clock on both
+	// BSD and Linux.
+	clock_gettime(CLOCK_MONOTONIC_PRECISE, &ts);
+#else
 	clock_gettime(CLOCK_MONOTONIC, &ts);
+#endif
 	return time_point(seconds(ts.tv_sec) + nanoseconds(ts.tv_nsec));
       }
 
@@ -233,7 +258,18 @@ namespace ceph {
 
       static time_point now() noexcept {
 	struct timespec ts;
+#if defined(CLOCK_MONOTONIC_COARSE)
+	// Linux systems have _COARSE clocks.
 	clock_gettime(CLOCK_MONOTONIC_COARSE, &ts);
+#elif defined(CLOCK_MONOTONIC_FAST)
+	// BSD systems have _FAST clocks.
+	clock_gettime(CLOCK_MONOTONIC_FAST, &ts);
+#else
+	// And if we find neither, you may wish to consult your system's
+	// documentation.
+#warning Falling back to CLOCK_MONOTONIC, may be slow.
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+#endif
 	return time_point(seconds(ts.tv_sec) + nanoseconds(ts.tv_nsec));
       }
     };