##// END OF EJS Templates
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

File last commit:

r38494:67dc32d4 @56 default
r38755:be498426 default
Show More
pointer.py
83 lines | 2.8 KiB | text/x-python | PythonLexer
# pointer.py - Git-LFS pointer serialization
#
# 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.
from __future__ import absolute_import
import re
from mercurial.i18n import _
from mercurial import (
error,
pycompat,
)
from mercurial.utils import (
stringutil,
)
class InvalidPointer(error.RevlogError):
pass
class gitlfspointer(dict):
VERSION = 'https://git-lfs.github.com/spec/v1'
def __init__(self, *args, **kwargs):
self['version'] = self.VERSION
super(gitlfspointer, self).__init__(*args)
self.update(pycompat.byteskwargs(kwargs))
@classmethod
def deserialize(cls, text):
try:
return cls(l.split(' ', 1) for l in text.splitlines()).validate()
except ValueError: # l.split returns 1 item instead of 2
raise InvalidPointer(_('cannot parse git-lfs text: %s')
% stringutil.pprint(text))
def serialize(self):
sortkeyfunc = lambda x: (x[0] != 'version', x)
items = sorted(self.validate().iteritems(), key=sortkeyfunc)
return ''.join('%s %s\n' % (k, v) for k, v in items)
def oid(self):
return self['oid'].split(':')[-1]
def size(self):
return int(self['size'])
# regular expressions used by _validate
# see https://github.com/git-lfs/git-lfs/blob/master/docs/spec.md
_keyre = re.compile(br'\A[a-z0-9.-]+\Z')
_valuere = re.compile(br'\A[^\n]*\Z')
_requiredre = {
'size': re.compile(br'\A[0-9]+\Z'),
'oid': re.compile(br'\Asha256:[0-9a-f]{64}\Z'),
'version': re.compile(br'\A%s\Z' % stringutil.reescape(VERSION)),
}
def validate(self):
"""raise InvalidPointer on error. return self if there is no error"""
requiredcount = 0
for k, v in self.iteritems():
if k in self._requiredre:
if not self._requiredre[k].match(v):
raise InvalidPointer(
_('unexpected lfs pointer value: %s=%s')
% (k, stringutil.pprint(v)))
requiredcount += 1
elif not self._keyre.match(k):
raise InvalidPointer(_('unexpected lfs pointer key: %s') % k)
if not self._valuere.match(v):
raise InvalidPointer(_('unexpected lfs pointer value: %s=%s')
% (k, stringutil.pprint(v)))
if len(self._requiredre) != requiredcount:
miss = sorted(set(self._requiredre.keys()).difference(self.keys()))
raise InvalidPointer(_('missing lfs pointer keys: %s')
% ', '.join(miss))
return self
deserialize = gitlfspointer.deserialize