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, 3 insertions, 3 deletions

diff --git a/rts/sm/GCThread.h b/rts/sm/GCThread.h
index e42a3a1239..b4f325631f 100644
--- a/rts/sm/GCThread.h
+++ b/rts/sm/GCThread.h
@@ -181,9 +181,9 @@ typedef struct gc_thread_ {
     lnat no_work;
     lnat scav_find_work;
 
-    Ticks gc_start_cpu;   // process CPU time
-    Ticks gc_start_elapsed;  // process elapsed time
-    Ticks gc_start_thread_cpu; // thread CPU time
+    Time gc_start_cpu;   // process CPU time
+    Time gc_start_elapsed;  // process elapsed time
+    Time gc_start_thread_cpu; // thread CPU time
     lnat gc_start_faults;
 
     // -------------------