Mercurial > hg
view contrib/check-py3-compat.py @ 38732:be4984261611
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
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 18 Jul 2018 09:49:34 -0700 |
parents | 778dc37ce683 |
children | 01417ca7f2e2 |
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#!/usr/bin/env python # # check-py3-compat - check Python 3 compatibility of Mercurial files # # Copyright 2015 Gregory Szorc <gregory.szorc@gmail.com> # # 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 ast import importlib import os import sys import traceback def check_compat_py2(f): """Check Python 3 compatibility for a file with Python 2""" with open(f, 'rb') as fh: content = fh.read() root = ast.parse(content) # Ignore empty files. if not root.body: return futures = set() haveprint = False for node in ast.walk(root): if isinstance(node, ast.ImportFrom): if node.module == '__future__': futures |= set(n.name for n in node.names) elif isinstance(node, ast.Print): haveprint = True if 'absolute_import' not in futures: print('%s not using absolute_import' % f) if haveprint and 'print_function' not in futures: print('%s requires print_function' % f) def check_compat_py3(f): """Check Python 3 compatibility of a file with Python 3.""" with open(f, 'rb') as fh: content = fh.read() try: ast.parse(content) except SyntaxError as e: print('%s: invalid syntax: %s' % (f, e)) return # Try to import the module. # For now we only support modules in packages because figuring out module # paths for things not in a package can be confusing. if (f.startswith(('hgdemandimport/', 'hgext/', 'mercurial/')) and not f.endswith('__init__.py')): assert f.endswith('.py') name = f.replace('/', '.')[:-3] try: importlib.import_module(name) except Exception as e: exc_type, exc_value, tb = sys.exc_info() # We walk the stack and ignore frames from our custom importer, # import mechanisms, and stdlib modules. This kinda/sorta # emulates CPython behavior in import.c while also attempting # to pin blame on a Mercurial file. for frame in reversed(traceback.extract_tb(tb)): if frame.name == '_call_with_frames_removed': continue if 'importlib' in frame.filename: continue if 'mercurial/__init__.py' in frame.filename: continue if frame.filename.startswith(sys.prefix): continue break if frame.filename: filename = os.path.basename(frame.filename) print('%s: error importing: <%s> %s (error at %s:%d)' % ( f, type(e).__name__, e, filename, frame.lineno)) else: print('%s: error importing module: <%s> %s (line %d)' % ( f, type(e).__name__, e, frame.lineno)) if __name__ == '__main__': if sys.version_info[0] == 2: fn = check_compat_py2 else: fn = check_compat_py3 for f in sys.argv[1:]: fn(f) sys.exit(0)