Mercurial > hg
view contrib/genosxversion.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 | 283a7da602ae |
children | 25880ddf9a86 |
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#!/usr/bin/env python2 from __future__ import absolute_import, print_function import argparse import json import os import subprocess import sys # Always load hg libraries from the hg we can find on $PATH. hglib = json.loads(subprocess.check_output( ['hg', 'debuginstall', '-Tjson']))[0]['hgmodules'] sys.path.insert(0, os.path.dirname(hglib)) from mercurial import util ap = argparse.ArgumentParser() ap.add_argument('--paranoid', action='store_true', help=("Be paranoid about how version numbers compare and " "produce something that's more likely to sort " "reasonably.")) ap.add_argument('--selftest', action='store_true', help='Run self-tests.') ap.add_argument('versionfile', help='Path to a valid mercurial __version__.py') def paranoidver(ver): """Given an hg version produce something that distutils can sort. Some Mac package management systems use distutils code in order to figure out upgrades, which makes life difficult. The test case is a reduced version of code in the Munki tool used by some large organizations to centrally manage OS X packages, which is what inspired this kludge. >>> paranoidver('3.4') '3.4.0' >>> paranoidver('3.4.2') '3.4.2' >>> paranoidver('3.0-rc+10') '2.9.9999-rc+10' >>> paranoidver('4.2+483-5d44d7d4076e') '4.2.0+483-5d44d7d4076e' >>> paranoidver('4.2.1+598-48d1e1214d8c') '4.2.1+598-48d1e1214d8c' >>> paranoidver('4.3-rc') '4.2.9999-rc' >>> paranoidver('4.3') '4.3.0' >>> from distutils import version >>> class LossyPaddedVersion(version.LooseVersion): ... '''Subclass version.LooseVersion to compare things like ... "10.6" and "10.6.0" as equal''' ... def __init__(self, s): ... self.parse(s) ... ... def _pad(self, version_list, max_length): ... 'Pad a version list by adding extra 0 components to the end' ... # copy the version_list so we don't modify it ... cmp_list = list(version_list) ... while len(cmp_list) < max_length: ... cmp_list.append(0) ... return cmp_list ... ... def __cmp__(self, other): ... if isinstance(other, str): ... other = MunkiLooseVersion(other) ... max_length = max(len(self.version), len(other.version)) ... self_cmp_version = self._pad(self.version, max_length) ... other_cmp_version = self._pad(other.version, max_length) ... return cmp(self_cmp_version, other_cmp_version) >>> def testver(older, newer): ... o = LossyPaddedVersion(paranoidver(older)) ... n = LossyPaddedVersion(paranoidver(newer)) ... return o < n >>> testver('3.4', '3.5') True >>> testver('3.4.0', '3.5-rc') True >>> testver('3.4-rc', '3.5') True >>> testver('3.4-rc+10-deadbeef', '3.5') True >>> testver('3.4.2', '3.5-rc') True >>> testver('3.4.2', '3.5-rc+10-deadbeef') True >>> testver('4.2+483-5d44d7d4076e', '4.2.1+598-48d1e1214d8c') True >>> testver('4.3-rc', '4.3') True >>> testver('4.3', '4.3-rc') False """ major, minor, micro, extra = util.versiontuple(ver, n=4) if micro is None: micro = 0 if extra: if extra.startswith('rc'): if minor == 0: major -= 1 minor = 9 else: minor -= 1 micro = 9999 extra = '-' + extra else: extra = '+' + extra else: extra = '' return '%d.%d.%d%s' % (major, minor, micro, extra) def main(argv): opts = ap.parse_args(argv[1:]) if opts.selftest: import doctest doctest.testmod() return with open(opts.versionfile) as f: for l in f: if l.startswith('version = '): # version number is entire line minus the quotes ver = l[len('version = ') + 1:-2] break if opts.paranoid: print(paranoidver(ver)) else: print(ver) if __name__ == '__main__': main(sys.argv)