perf: clear vfs audit_cache before each run
When generating a stream clone, we spend a large amount of time auditing path.
Before this changes, the first run was warming the vfs cache for the other
runs, leading to a large runtime difference and a "faulty" reported timing for
the operation.
We now clear this important cache between run to get a more realistic timing.
Below are some example of median time change when clearing these cases. The
maximum time for a run did not changed significantly.
### data-env-vars.name = mozilla-central-2018-08-01-zstd-sparse-revlog
# benchmark.name = hg.perf.exchange.stream.generate
# bin-env-vars.hg.flavor = default
# bin-env-vars.hg.py-re2-module = default
# benchmark.variants.version = latest
no-clearing: 17.289905
cache-clearing: 21.587965 (+24.86%, +4.30)
## data-env-vars.name = mozilla-central-2024-03-22-zstd-sparse-revlog
no-clearing: 32.670748
cache-clearing: 40.467095 (+23.86%, +7.80)
## data-env-vars.name = mozilla-try-2019-02-18-zstd-sparse-revlog
no-clearing: 37.838858
cache-clearing: 46.072749 (+21.76%, +8.23)
## data-env-vars.name = mozilla-unified-2024-03-22-zstd-sparse-revlog
no-clearing: 32.969395
cache-clearing: 39.646209 (+20.25%, +6.68)
In addition, this significantly reduce the timing difference between the
performance command, from the perf extensions and a `real `hg bundle` call
producing a stream bundle. Some significant differences remain especially on
the "mozilla-try" repositories, but they are now smaller.
Note that some of that difference will actually not be
attributable to the stream generation (like maybe phases or branch map
computation).
Below are some benchmarks done on a currently draft changeset fixing some
unrelated slowness in `hg bundle` (34a78972af409d1ff37c29e60f6ca811ad1a457d)
### data-env-vars.name = mozilla-central-2018-08-01-zstd-sparse-revlog
# bin-env-vars.hg.flavor = default
# bin-env-vars.hg.py-re2-module = default
hg.perf.exchange.stream.generate: 21.587965
hg.command.bundle: 24.301799 (+12.57%, +2.71)
## data-env-vars.name = mozilla-central-2024-03-22-zstd-sparse-revlog
hg.perf.exchange.stream.generate: 40.467095
hg.command.bundle: 44.831317 (+10.78%, +4.36)
## data-env-vars.name = mozilla-unified-2024-03-22-zstd-sparse-revlog
hg.perf.exchange.stream.generate: 39.646209
hg.command.bundle: 45.395258 (+14.50%, +5.75)
## data-env-vars.name = mozilla-try-2019-02-18-zstd-sparse-revlog
hg.perf.exchange.stream.generate: 46.072749
hg.command.bundle: 55.882608 (+21.29%, +9.81)
## data-env-vars.name = mozilla-try-2023-03-22-zlib-general-delta
hg.perf.exchange.stream.generate: 334.716708
hg.command.bundle: 377.856767 (+12.89%, +43.14)
## data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog
hg.perf.exchange.stream.generate: 302.972301
hg.command.bundle: 326.098755 (+7.63%, +23.13)
# demandimportpy3 - global demand-loading of modules for Mercurial
#
# Copyright 2017 Facebook Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""Lazy loading for Python 3.6 and above.
This uses the new importlib finder/loader functionality available in Python 3.5
and up. The code reuses most of the mechanics implemented inside importlib.util,
but with a few additions:
* Allow excluding certain modules from lazy imports.
* Expose an interface that's substantially the same as demandimport for
Python 2.
This also has some limitations compared to the Python 2 implementation:
* Much of the logic is per-package, not per-module, so any packages loaded
before demandimport is enabled will not be lazily imported in the future. In
practice, we only expect builtins to be loaded before demandimport is
enabled.
"""
import contextlib
import importlib.util
import sys
from . import tracing
_deactivated = False
class _lazyloaderex(importlib.util.LazyLoader):
"""This is a LazyLoader except it also follows the _deactivated global and
the ignore list.
"""
_HAS_DYNAMIC_ATTRIBUTES = True # help pytype not flag self.loader
def exec_module(self, module):
"""Make the module load lazily."""
with tracing.log('demandimport %s', module):
if _deactivated or module.__name__ in ignores:
# Reset the loader on the module as super() does (issue6725)
module.__spec__.loader = self.loader
module.__loader__ = self.loader
self.loader.exec_module(module)
else:
super().exec_module(module)
class LazyFinder:
"""A wrapper around a ``MetaPathFinder`` that makes loaders lazy.
``sys.meta_path`` finders have their ``find_spec()`` called to locate a
module. This returns a ``ModuleSpec`` if found or ``None``. The
``ModuleSpec`` has a ``loader`` attribute, which is called to actually
load a module.
Our class wraps an existing finder and overloads its ``find_spec()`` to
replace the ``loader`` with our lazy loader proxy.
We have to use __getattribute__ to proxy the instance because some meta
path finders don't support monkeypatching.
"""
__slots__ = ("_finder",)
def __init__(self, finder):
object.__setattr__(self, "_finder", finder)
def __repr__(self):
return "<LazyFinder for %r>" % object.__getattribute__(self, "_finder")
# __bool__ is canonical Python 3. But check-code insists on __nonzero__ being
# defined via `def`.
def __nonzero__(self):
return bool(object.__getattribute__(self, "_finder"))
__bool__ = __nonzero__
def __getattribute__(self, name):
if name in ("_finder", "find_spec"):
return object.__getattribute__(self, name)
return getattr(object.__getattribute__(self, "_finder"), name)
def __delattr__(self, name):
return delattr(object.__getattribute__(self, "_finder"), name)
def __setattr__(self, name, value):
return setattr(object.__getattribute__(self, "_finder"), name, value)
def find_spec(self, fullname, path, target=None):
finder = object.__getattribute__(self, "_finder")
try:
find_spec = finder.find_spec
except AttributeError:
loader = finder.find_module(fullname, path)
if loader is None:
spec = None
else:
spec = importlib.util.spec_from_loader(fullname, loader)
else:
spec = find_spec(fullname, path, target)
# Lazy loader requires exec_module().
if (
spec is not None
and spec.loader is not None
and getattr(spec.loader, "exec_module", None)
):
spec.loader = _lazyloaderex(spec.loader)
return spec
ignores = set()
def init(ignoreset):
global ignores
ignores = ignoreset
def isenabled():
return not _deactivated and any(
isinstance(finder, LazyFinder) for finder in sys.meta_path
)
def disable():
new_finders = []
for finder in sys.meta_path:
new_finders.append(
finder._finder if isinstance(finder, LazyFinder) else finder
)
sys.meta_path[:] = new_finders
def enable():
new_finders = []
for finder in sys.meta_path:
new_finders.append(
LazyFinder(finder) if not isinstance(finder, LazyFinder) else finder
)
sys.meta_path[:] = new_finders
@contextlib.contextmanager
def deactivated():
# This implementation is a bit different from Python 2's. Python 3
# maintains a per-package finder cache in sys.path_importer_cache (see
# PEP 302). This means that we can't just call disable + enable.
# If we do that, in situations like:
#
# demandimport.enable()
# ...
# from foo.bar import mod1
# with demandimport.deactivated():
# from foo.bar import mod2
#
# mod2 will be imported lazily. (The converse also holds -- whatever finder
# first gets cached will be used.)
#
# Instead, have a global flag the LazyLoader can use.
global _deactivated
demandenabled = isenabled()
if demandenabled:
_deactivated = True
try:
yield
finally:
if demandenabled:
_deactivated = False