stream-clone: disable gc for `_entries_walk` duration
The number of small container created turn Python in a gc-frenzy that seriously
impact performance.
This significantly boost performance. The following number comes from a large
private repository using perf::stream-locked-section:
base-line: 35.04 seconds
prev-change: 24.51 seconds (-30%)
this-change: 20.88 seconds (-40% from baseline; -15% from previous changes)
# Support code for event tracing in Mercurial. Lives in demandimport
# so it can also be used in demandimport.
#
# Copyright 2018 Google LLC.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
import contextlib
import os
_pipe = None
_checked = False
_session = 'none'
def _isactive():
global _pipe, _session, _checked
if _pipe is None:
if _checked:
return False
_checked = True
if 'HGCATAPULTSERVERPIPE' not in os.environ:
return False
_pipe = open(os.environ['HGCATAPULTSERVERPIPE'], 'w', 1)
_session = os.environ.get('HGCATAPULTSESSION', 'none')
return True
@contextlib.contextmanager
def log(whencefmt, *whenceargs):
if not _isactive():
yield
return
whence = whencefmt % whenceargs
try:
# Both writes to the pipe are wrapped in try/except to ignore
# errors, as we can see mysterious errors in here if the pager
# is active. Presumably other conditions could trigger
# problems too.
try:
_pipe.write('START %s %s\n' % (_session, whence))
except IOError:
pass
yield
finally:
try:
_pipe.write('END %s %s\n' % (_session, whence))
except IOError:
pass
def counter(label, amount, *labelargs):
if not _isactive():
return
l = label % labelargs
# See above in log() for why this is in a try/except.
try:
_pipe.write('COUNTER %s %d %s\n' % (_session, amount, l))
except IOError:
pass