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, 4 insertions, 10 deletions

diff --git a/rts/GetTime.h b/rts/GetTime.h
index b8d402db7c..86c5511df9 100644
--- a/rts/GetTime.h
+++ b/rts/GetTime.h
@@ -11,16 +11,10 @@
 
 #include "BeginPrivate.h"
 
-// We'll use a fixed resolution of usec for now.  The machine
-// dependent implementation may have a different resolution, but we'll
-// normalise to this for the machine independent interface.
-#define TICKS_PER_SECOND 1000000
-typedef StgInt64 Ticks;
-
-Ticks getProcessCPUTime     (void);
-Ticks getThreadCPUTime      (void);
-Ticks getProcessElapsedTime (void);
-void  getProcessTimes       (Ticks *user, Ticks *elapsed);
+Time getProcessCPUTime     (void);
+Time getThreadCPUTime      (void);
+Time getProcessElapsedTime (void);
+void getProcessTimes       (Time *user, Time *elapsed);
 
 /* Get the current date and time.
    Uses seconds since the Unix epoch, plus nanoseconds