profile: introduce a knob to control if the context is actually profiling

This is a step toward allowing context where the profiling in enabled
withing the context range.

This also open the way to kill the dedicated "maybeprofile" context manager
and keep only one of 'profile' and 'maybeprofile'.

mercurial/profiling.py

@@ -1,235 +1,234 b''
 # profiling.py - profiling functions
 #
 # Copyright 2016 Gregory Szorc <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import, print_function
 
 import contextlib
 
 from .i18n import _
 from . import (
     encoding,
     error,
     extensions,
     util,
 )
 
 def _loadprofiler(ui, profiler):
     """load profiler extension. return profile method, or None on failure"""
     extname = profiler
     extensions.loadall(ui, whitelist=[extname])
     try:
         mod = extensions.find(extname)
     except KeyError:
         return None
     else:
         return getattr(mod, 'profile', None)
 
 @contextlib.contextmanager
 def lsprofile(ui, fp):
     format = ui.config('profiling', 'format', default='text')
     field = ui.config('profiling', 'sort', default='inlinetime')
     limit = ui.configint('profiling', 'limit', default=30)
     climit = ui.configint('profiling', 'nested', default=0)
 
     if format not in ['text', 'kcachegrind']:
         ui.warn(_("unrecognized profiling format '%s'"
                     " - Ignored\n") % format)
         format = 'text'
 
     try:
         from . import lsprof
     except ImportError:
         raise error.Abort(_(
             'lsprof not available - install from '
             'http://codespeak.net/svn/user/arigo/hack/misc/lsprof/'))
     p = lsprof.Profiler()
     p.enable(subcalls=True)
     try:
         yield
     finally:
         p.disable()
 
         if format == 'kcachegrind':
             from . import lsprofcalltree
             calltree = lsprofcalltree.KCacheGrind(p)
             calltree.output(fp)
         else:
             # format == 'text'
             stats = lsprof.Stats(p.getstats())
             stats.sort(field)
             stats.pprint(limit=limit, file=fp, climit=climit)
 
 @contextlib.contextmanager
 def flameprofile(ui, fp):
     try:
         from flamegraph import flamegraph
     except ImportError:
         raise error.Abort(_(
             'flamegraph not available - install from '
             'https://github.com/evanhempel/python-flamegraph'))
     # developer config: profiling.freq
     freq = ui.configint('profiling', 'freq', default=1000)
     filter_ = None
     collapse_recursion = True
     thread = flamegraph.ProfileThread(fp, 1.0 / freq,
                                       filter_, collapse_recursion)
     start_time = util.timer()
     try:
         thread.start()
         yield
     finally:
         thread.stop()
         thread.join()
         print('Collected %d stack frames (%d unique) in %2.2f seconds.' % (
             util.timer() - start_time, thread.num_frames(),
             thread.num_frames(unique=True)))
 
 @contextlib.contextmanager
 def statprofile(ui, fp):
     from . import statprof
 
     freq = ui.configint('profiling', 'freq', default=1000)
     if freq > 0:
         # Cannot reset when profiler is already active. So silently no-op.
         if statprof.state.profile_level == 0:
             statprof.reset(freq)
     else:
         ui.warn(_("invalid sampling frequency '%s' - ignoring\n") % freq)
 
     statprof.start(mechanism='thread')
 
     try:
         yield
     finally:
         data = statprof.stop()
 
         profformat = ui.config('profiling', 'statformat', 'hotpath')
 
         formats = {
             'byline': statprof.DisplayFormats.ByLine,
             'bymethod': statprof.DisplayFormats.ByMethod,
             'hotpath': statprof.DisplayFormats.Hotpath,
             'json': statprof.DisplayFormats.Json,
             'chrome': statprof.DisplayFormats.Chrome,
         }
 
         if profformat in formats:
             displayformat = formats[profformat]
         else:
             ui.warn(_('unknown profiler output format: %s\n') % profformat)
             displayformat = statprof.DisplayFormats.Hotpath
 
         kwargs = {}
 
         def fraction(s):
             if s.endswith('%'):
                 v = float(s[:-1]) / 100
             else:
                 v = float(s)
             if 0 <= v <= 1:
                 return v
             raise ValueError(s)
 
         if profformat == 'chrome':
             showmin = ui.configwith(fraction, 'profiling', 'showmin', 0.005)
             showmax = ui.configwith(fraction, 'profiling', 'showmax', 0.999)
             kwargs.update(minthreshold=showmin, maxthreshold=showmax)
 
         statprof.display(fp, data=data, format=displayformat, **kwargs)
 
 class profile(object):
     """Start profiling.
 
     Profiling is active when the context manager is active. When the context
     manager exits, profiling results will be written to the configured output.
     """
-    def __init__(self, ui):
+    def __init__(self, ui, enabled=True):
         self._ui = ui
         self._output = None
         self._fp = None
         self._profiler = None
+        self._enabled = enabled
         self._entered = False
         self._started = False
 
     def __enter__(self):
         self._entered = True
-        self.start()
+        if self._enabled:
+            self.start()
 
     def start(self):
         """Start profiling.
 
         The profiling will stop at the context exit.
 
         If the profiler was already started, this has no effect."""
         if not self._entered:
             raise error.ProgrammingError()
         if self._started:
             return
         self._started = True
         profiler = encoding.environ.get('HGPROF')
         proffn = None
         if profiler is None:
             profiler = self._ui.config('profiling', 'type', default='stat')
         if profiler not in ('ls', 'stat', 'flame'):
             # try load profiler from extension with the same name
             proffn = _loadprofiler(self._ui, profiler)
             if proffn is None:
                 self._ui.warn(_("unrecognized profiler '%s' - ignored\n")
                               % profiler)
                 profiler = 'stat'
 
         self._output = self._ui.config('profiling', 'output')
 
         if self._output == 'blackbox':
             self._fp = util.stringio()
         elif self._output:
             path = self._ui.expandpath(self._output)
             self._fp = open(path, 'wb')
         else:
             self._fp = self._ui.ferr
 
         if proffn is not None:
             pass
         elif profiler == 'ls':
             proffn = lsprofile
         elif profiler == 'flame':
             proffn = flameprofile
         else:
             proffn = statprofile
 
         self._profiler = proffn(self._ui, self._fp)
         self._profiler.__enter__()
 
     def __exit__(self, exception_type, exception_value, traceback):
         if self._profiler is None:
             return
         self._profiler.__exit__(exception_type, exception_value, traceback)
         if self._output:
             if self._output == 'blackbox':
                 val = 'Profile:\n%s' % self._fp.getvalue()
                 # ui.log treats the input as a format string,
                 # so we need to escape any % signs.
                 val = val.replace('%', '%%')
                 self._ui.log('profile', val)
             self._fp.close()
 
 @contextlib.contextmanager
 def maybeprofile(ui):
     """Profile if enabled, else do nothing.
 
     This context manager can be used to optionally profile if profiling
     is enabled. Otherwise, it does nothing.
 
     The purpose of this context manager is to make calling code simpler:
     just use a single code path for calling into code you may want to profile
     and this function determines whether to start profiling.
     """
-    if ui.configbool('profiling', 'enabled'):
-        with profile(ui):
-            yield
-    else:
+    with profile(ui, enabled=ui.configbool('profiling', 'enabled')):
         yield