profiling: introduce a "profiling.time-track" option

profiling: introduce a "profiling.time-track" option

This option allows to switch the time used by the statistical profiler from
cpu to real time. Our goal is to profile IO intensive operations using the
mercurial profiler.

--- a/mercurial/configitems.py	Fri Jun 01 11:23:27 2018 +0200
+++ b/mercurial/configitems.py	Fri Jun 01 17:27:58 2018 +0200
@@ -867,6 +867,9 @@
 coreconfigitem('profiling', 'statformat',
     default='hotpath',
 )
+coreconfigitem('profiling', 'time-track',
+    default='cpu',
+)
 coreconfigitem('profiling', 'type',
     default='stat',
 )

--- a/mercurial/help/config.txt	Fri Jun 01 11:23:27 2018 +0200
+++ b/mercurial/help/config.txt	Fri Jun 01 17:27:58 2018 +0200
@@ -1652,6 +1652,10 @@
     ``inlinetime``.
     (default: inlinetime)
 
+``time-track``
+    Control if the stat profiler track ``cpu`` or ``real`` time.
+    (default: ``cpu``)
+
 ``limit``
     Number of lines to show. Specific to the ``ls`` instrumenting profiler.
     (default: 30)

--- a/mercurial/profiling.py	Fri Jun 01 11:23:27 2018 +0200
+++ b/mercurial/profiling.py	Fri Jun 01 17:27:58 2018 +0200
@@ -101,7 +101,8 @@
     else:
         ui.warn(_("invalid sampling frequency '%s' - ignoring\n") % freq)
 
-    statprof.start(mechanism='thread')
+    track = ui.config('profiling', 'time-track')
+    statprof.start(mechanism='thread', track=track)
 
     try:
         yield

--- a/mercurial/statprof.py	Fri Jun 01 11:23:27 2018 +0200
+++ b/mercurial/statprof.py	Fri Jun 01 17:27:58 2018 +0200
@@ -148,6 +148,7 @@
 class ProfileState(object):
     def __init__(self, frequency=None):
         self.reset(frequency)
+        self.track = 'cpu'
 
     def reset(self, frequency=None):
         # total so far
@@ -180,7 +181,13 @@
         )
 
     def seconds_per_sample(self):
-        return self.accumulated_time[0] / len(self.samples)
+        return self.accumulated_time[self.timeidx] / len(self.samples)
+
+    @property
+    def timeidx(self):
+        if self.track == 'real':
+            return 1
+        return 0
 
 state = ProfileState()
 
@@ -268,7 +275,8 @@
         now = clock()
         state.accumulate_time(now)
 
-        state.samples.append(Sample.from_frame(frame, state.accumulated_time[0]))
+        timestamp = state.accumulated_time[state.timeidx]
+        state.samples.append(Sample.from_frame(frame, timestamp))
 
         signal.setitimer(signal.ITIMER_PROF,
             state.sample_interval, 0.0)
@@ -281,7 +289,9 @@
         state.accumulate_time(now)
 
         frame = sys._current_frames()[tid]
-        state.samples.append(Sample.from_frame(frame, state.accumulated_time[0]))
+
+        timestamp = state.accumulated_time[state.timeidx]
+        state.samples.append(Sample.from_frame(frame, timestamp))
 
         state.last_start_time = now
         time.sleep(state.sample_interval)
@@ -295,8 +305,9 @@
     return state.profile_level > 0
 
 lastmechanism = None
-def start(mechanism='thread'):
+def start(mechanism='thread', track='cpu'):
     '''Install the profiling signal handler, and start profiling.'''
+    state.track = track # note: nesting different mode won't work
     state.profile_level += 1
     if state.profile_level == 1:
         state.last_start_time = clock()