Time handling overhaul

Terminology cleanup: the type "Ticks" has been renamed "Time", which
is an StgWord64 in units of TIME_RESOLUTION (currently nanoseconds).
The terminology "tick" is now used consistently to mean the interval
between timer signals.

The ticker now always ticks in realtime (actually CLOCK_MONOTONIC if
we have it).  Before it used CPU time in the non-threaded RTS and
realtime in the threaded RTS, but I've discovered that the CPU timer
has terrible resolution (at least on Linux) and isn't much use for
profiling.  So now we always use realtime.  This should also fix

The default tick interval is now 10ms, except when profiling where we
drop it to 1ms.  This gives more accurate profiles without affecting
runtime too much (<1%).

Lots of cleanups - the resolution of Time is now in one place
only (Rts.h) rather than having calculations that depend on the
resolution scattered all over the RTS.  I hope I found them all.

1 files changed, 30 insertions, 0 deletions

diff --git a/includes/Rts.h b/includes/Rts.h
index 5caba59dbe..45c09f8fb7 100644
--- a/includes/Rts.h
+++ b/includes/Rts.h
@@ -155,6 +155,36 @@ void _assertFail(const char *filename, unsigned int linenum)
 #endif
 
 /* -----------------------------------------------------------------------------
+   Time values in the RTS
+   -------------------------------------------------------------------------- */
+
+// For most time values in the RTS we use a fixed resolution of nanoseconds,
+// normalising the time we get from platform-dependent APIs to this
+// resolution.
+#define TIME_RESOLUTION 1000000000
+typedef StgInt64 Time;
+
+#if TIME_RESOLUTION == 1000000000
+// I'm being lazy, but it's awkward to define fully general versions of these
+#define TimeToUS(t)      (t / 1000)
+#define TimeToNS(t)      (t)
+#define USToTime(t)      ((Time)(t) * 1000)
+#define NSToTime(t)      ((Time)(t))
+#else
+#error Fix TimeToNS(), TimeToUS() etc.
+#endif
+
+#define SecondsToTime(t) ((Time)(t) * TIME_RESOLUTION)
+#define TimeToSeconds(t) ((t) / TIME_RESOLUTION)
+
+// Use instead of SecondsToTime() when we have a floating-point
+// seconds value, to avoid truncating it.
+INLINE_HEADER Time fsecondsToTime (double t)
+{
+    return (Time)(t * TIME_RESOLUTION);
+}
+
+/* -----------------------------------------------------------------------------
    Include everything STG-ish
    -------------------------------------------------------------------------- */