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merge: mark file gets as not thread safe (issue5933)...
merge: mark file gets as not thread safe (issue5933) In default installs, this has the effect of disabling the thread-based worker on Windows when manifesting files in the working directory. My measurements have shown that with revlog-based repositories, Mercurial spends a lot of CPU time in revlog code resolving file data. This ends up incurring a lot of context switching across threads and slows down `hg update` operations when going from an empty working directory to the tip of the repo. On mozilla-unified (246,351 files) on an i7-6700K (4+4 CPUs): before: 487s wall after: 360s wall (equivalent to worker.enabled=false) cpus=2: 379s wall Even with only 2 threads, the thread pool is still slower. The introduction of the thread-based worker (02b36e860e0b) states that it resulted in a "~50%" speedup for `hg sparse --enable-profile` and `hg sparse --disable-profile`. This disagrees with my measurement above. I theorize a few reasons for this: 1) Removal of files from the working directory is I/O - not CPU - bound and should benefit from a thread pool (unless I/O is insanely fast and the GIL release is near instantaneous). So tests like `hg sparse --enable-profile` may exercise deletion throughput and aren't good benchmarks for worker tasks that are CPU heavy. 2) The patch was authored by someone at Facebook. The results were likely measured against a repository using remotefilelog. And I believe that revision retrieval during working directory updates with remotefilelog will often use a remote store, thus being I/O and not CPU bound. This probably resulted in an overstated performance gain. Since there appears to be a need to enable the thread-based worker with some stores, I've made the flagging of file gets as thread safe configurable. I've made it experimental because I don't want to formalize a boolean flag for this option and because this attribute is best captured against the store implementation. But we don't have a proper store API for this yet. I'd rather cross this bridge later. It is possible there are revlog-based repositories that do benefit from a thread-based worker. I didn't do very comprehensive testing. If there are, we may want to devise a more proper algorithm for whether to use the thread-based worker, including possibly config options to limit the number of threads to use. But until I see evidence that justifies complexity, simplicity wins. Differential Revision: https://phab.mercurial-scm.org/D3963

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setup.py
97 lines | 2.7 KiB | text/x-python | PythonLexer
#!/usr/bin/env python
# Copyright (c) 2016-present, Gregory Szorc
# All rights reserved.
#
# This software may be modified and distributed under the terms
# of the BSD license. See the LICENSE file for details.
import os
import sys
from setuptools import setup
try:
import cffi
except ImportError:
cffi = None
import setup_zstd
SUPPORT_LEGACY = False
SYSTEM_ZSTD = False
WARNINGS_AS_ERRORS = False
if os.environ.get('ZSTD_WARNINGS_AS_ERRORS', ''):
WARNINGS_AS_ERRORS = True
if '--legacy' in sys.argv:
SUPPORT_LEGACY = True
sys.argv.remove('--legacy')
if '--system-zstd' in sys.argv:
SYSTEM_ZSTD = True
sys.argv.remove('--system-zstd')
if '--warnings-as-errors' in sys.argv:
WARNINGS_AS_ERRORS = True
sys.argv.remove('--warning-as-errors')
# Code for obtaining the Extension instance is in its own module to
# facilitate reuse in other projects.
extensions = [
setup_zstd.get_c_extension(name='zstd',
support_legacy=SUPPORT_LEGACY,
system_zstd=SYSTEM_ZSTD,
warnings_as_errors=WARNINGS_AS_ERRORS),
]
install_requires = []
if cffi:
import make_cffi
extensions.append(make_cffi.ffi.distutils_extension())
# Need change in 1.10 for ffi.from_buffer() to handle all buffer types
# (like memoryview).
# Need feature in 1.11 for ffi.gc() to declare size of objects so we avoid
# garbage collection pitfalls.
install_requires.append('cffi>=1.11')
version = None
with open('c-ext/python-zstandard.h', 'r') as fh:
for line in fh:
if not line.startswith('#define PYTHON_ZSTANDARD_VERSION'):
continue
version = line.split()[2][1:-1]
break
if not version:
raise Exception('could not resolve package version; '
'this should never happen')
setup(
name='zstandard',
version=version,
description='Zstandard bindings for Python',
long_description=open('README.rst', 'r').read(),
url='https://github.com/indygreg/python-zstandard',
author='Gregory Szorc',
author_email='gregory.szorc@gmail.com',
license='BSD',
classifiers=[
'Development Status :: 4 - Beta',
'Intended Audience :: Developers',
'License :: OSI Approved :: BSD License',
'Programming Language :: C',
'Programming Language :: Python :: 2.7',
'Programming Language :: Python :: 3.4',
'Programming Language :: Python :: 3.5',
'Programming Language :: Python :: 3.6',
],
keywords='zstandard zstd compression',
packages=['zstandard'],
ext_modules=extensions,
test_suite='tests',
install_requires=install_requires,
)