Mercurial > hg
view tests/test-demandimport.py @ 47802:de2e04fe4897
hgwebdir: avoid systematic full garbage collection
Forcing a systematic full garbage collection upon each request
can serioulsy harm performance. This is reported as
https://bz.mercurial-scm.org/show_bug.cgi?id=6075
With this change we're performing the full collection according
to a new setting, `experimental.web.full-garbage-collection-rate`.
The default value is 1, which doesn't change the behavior and will
allow us to test on real use cases. If the value is 0, no full garbage
collection occurs.
Regardless of the value of the setting, a partial garbage collection
still occurs upon each request (not attempting to collect objects from
the oldest generation). This should be enough to take care of
reference cycles that have been created by the last request
(assessment of this requires changing the setting, not to be 1).
In my experience chasing memory leaks in Mercurial servers,
the full collection never reclaimed any memory, but this is with
Python 3 and biased towards small repositories.
On the other hand, as explained in the Python developer docs [1],
frequent full collections are very harmful in terms of performance if
lots of objects survive the collection, and hence stay in the
oldest generation. Note that `gc.collect()` is indeed trying to
collect the oldest generation [2]. This happens usually in two cases:
- unwanted lingering objects (i.e., an actual memory leak that
the GC cannot do anything about). Sadly, we have lots of those
these days.
- desireable long-term objects, typically in caches (not inner caches
carried by repositories, which should be collected with them). This
is a subject of interest for the Heptapod project.
In short, the flat rate that this change still permits is
probably a bad idea in most cases, and the default value can
be tweaked later on (or even be set to 0) according to experiments
in the wild.
The test is inspired from test-hgwebdir-paths.py
[1] https://devguide.python.org/garbage_collector/#collecting-the-oldest-generation
[2] https://docs.python.org/3/library/gc.html#gc.collect
Differential Revision: https://phab.mercurial-scm.org/D11204
author | Georges Racinet <georges.racinet@octobus.net> |
---|---|
date | Tue, 20 Jul 2021 17:20:19 +0200 |
parents | 0826d684a1b5 |
children | 6000f5b25c9b |
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from __future__ import absolute_import, print_function from mercurial import demandimport demandimport.enable() import os import subprocess import sys import types # Don't import pycompat because it has too many side-effects. ispy3 = sys.version_info[0] >= 3 # Only run if demandimport is allowed if subprocess.call( [os.environ['PYTHON'], '%s/hghave' % os.environ['TESTDIR'], 'demandimport'] ): sys.exit(80) # We rely on assert, which gets optimized out. if sys.flags.optimize: sys.exit(80) # The demand importer doesn't work on Python 3.5. if sys.version_info[0:2] == (3, 5): sys.exit(80) if ispy3: from importlib.util import _LazyModule try: from importlib.util import _Module as moduletype except ImportError: moduletype = types.ModuleType else: moduletype = types.ModuleType if os.name != 'nt': try: import distutils.msvc9compiler print( 'distutils.msvc9compiler needs to be an immediate ' 'importerror on non-windows platforms' ) distutils.msvc9compiler except ImportError: pass import re rsub = re.sub def f(obj): l = repr(obj) l = rsub("0x[0-9a-fA-F]+", "0x?", l) l = rsub("from '.*'", "from '?'", l) l = rsub("'<[a-z]*>'", "'<whatever>'", l) return l demandimport.disable() os.environ['HGDEMANDIMPORT'] = 'disable' # this enable call should not actually enable demandimport! demandimport.enable() from mercurial import node # We use assert instead of a unittest test case because having imports inside # functions changes behavior of the demand importer. if ispy3: assert not isinstance(node, _LazyModule) else: assert f(node) == "<module 'mercurial.node' from '?'>", f(node) # now enable it for real del os.environ['HGDEMANDIMPORT'] demandimport.enable() # Test access to special attributes through demandmod proxy assert 'mercurial.error' not in sys.modules from mercurial import error as errorproxy if ispy3: # unsure why this isn't lazy. assert not isinstance(f, _LazyModule) assert f(errorproxy) == "<module 'mercurial.error' from '?'>", f(errorproxy) else: assert f(errorproxy) == "<unloaded module 'error'>", f(errorproxy) doc = ' '.join(errorproxy.__doc__.split()[:3]) assert doc == 'Mercurial exceptions. This', doc assert errorproxy.__name__ == 'mercurial.error', errorproxy.__name__ # __name__ must be accessible via __dict__ so the relative imports can be # resolved name = errorproxy.__dict__['__name__'] assert name == 'mercurial.error', name if ispy3: assert not isinstance(errorproxy, _LazyModule) assert f(errorproxy) == "<module 'mercurial.error' from '?'>", f(errorproxy) else: assert f(errorproxy) == "<proxied module 'error'>", f(errorproxy) import os if ispy3: assert not isinstance(os, _LazyModule) assert f(os) == "<module 'os' from '?'>", f(os) else: assert f(os) == "<unloaded module 'os'>", f(os) assert f(os.system) == '<built-in function system>', f(os.system) assert f(os) == "<module 'os' from '?'>", f(os) assert 'mercurial.utils.procutil' not in sys.modules from mercurial.utils import procutil if ispy3: assert isinstance(procutil, _LazyModule) assert f(procutil) == "<module 'mercurial.utils.procutil' from '?'>", f( procutil ) else: assert f(procutil) == "<unloaded module 'procutil'>", f(procutil) assert f(procutil.system) == '<function system at 0x?>', f(procutil.system) assert procutil.__class__ == moduletype, procutil.__class__ assert f(procutil) == "<module 'mercurial.utils.procutil' from '?'>", f( procutil ) assert f(procutil.system) == '<function system at 0x?>', f(procutil.system) assert 'mercurial.hgweb' not in sys.modules from mercurial import hgweb if ispy3: assert isinstance(hgweb, _LazyModule) assert f(hgweb) == "<module 'mercurial.hgweb' from '?'>", f(hgweb) assert isinstance(hgweb.hgweb_mod, _LazyModule) assert ( f(hgweb.hgweb_mod) == "<module 'mercurial.hgweb.hgweb_mod' from '?'>" ), f(hgweb.hgweb_mod) else: assert f(hgweb) == "<unloaded module 'hgweb'>", f(hgweb) assert f(hgweb.hgweb_mod) == "<unloaded module 'hgweb_mod'>", f( hgweb.hgweb_mod ) assert f(hgweb) == "<module 'mercurial.hgweb' from '?'>", f(hgweb) import re as fred if ispy3: assert not isinstance(fred, _LazyModule) assert f(fred) == "<module 're' from '?'>" else: assert f(fred) == "<unloaded module 're'>", f(fred) import re as remod if ispy3: assert not isinstance(remod, _LazyModule) assert f(remod) == "<module 're' from '?'>" else: assert f(remod) == "<unloaded module 're'>", f(remod) import sys as re if ispy3: assert not isinstance(re, _LazyModule) assert f(re) == "<module 'sys' (built-in)>" else: assert f(re) == "<unloaded module 'sys'>", f(re) if ispy3: assert not isinstance(fred, _LazyModule) assert f(fred) == "<module 're' from '?'>", f(fred) else: assert f(fred) == "<unloaded module 're'>", f(fred) assert f(fred.sub) == '<function sub at 0x?>', f(fred.sub) if ispy3: assert not isinstance(fred, _LazyModule) assert f(fred) == "<module 're' from '?'>", f(fred) else: assert f(fred) == "<proxied module 're'>", f(fred) remod.escape # use remod assert f(remod) == "<module 're' from '?'>", f(remod) if ispy3: assert not isinstance(re, _LazyModule) assert f(re) == "<module 'sys' (built-in)>" assert f(type(re.stderr)) == "<class '_io.TextIOWrapper'>", f( type(re.stderr) ) assert f(re) == "<module 'sys' (built-in)>" else: assert f(re) == "<unloaded module 'sys'>", f(re) assert f(re.stderr) == "<open file '<whatever>', mode 'w' at 0x?>", f( re.stderr ) assert f(re) == "<proxied module 'sys'>", f(re) assert 'telnetlib' not in sys.modules import telnetlib if ispy3: assert isinstance(telnetlib, _LazyModule) assert f(telnetlib) == "<module 'telnetlib' from '?'>" else: assert f(telnetlib) == "<unloaded module 'telnetlib'>", f(telnetlib) try: from telnetlib import unknownattr assert False, ( 'no demandmod should be created for attribute of non-package ' 'module:\ntelnetlib.unknownattr = %s' % f(unknownattr) ) except ImportError as inst: assert rsub(r"'", '', str(inst)).startswith( 'cannot import name unknownattr' ) from mercurial import util # Unlike the import statement, __import__() function should not raise # ImportError even if fromlist has an unknown item # (see Python/import.c:import_module_level() and ensure_fromlist()) assert 'ftplib' not in sys.modules zipfileimp = __import__('ftplib', globals(), locals(), ['unknownattr']) assert f(zipfileimp) == "<module 'ftplib' from '?'>", f(zipfileimp) assert not util.safehasattr(zipfileimp, 'unknownattr')