Mercurial > hg
view tests/test-simplekeyvaluefile.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 | 6eca47f6319d |
children | aaad36b88298 |
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from __future__ import absolute_import import unittest import silenttestrunner from mercurial import ( error, scmutil, ) class mockfile(object): def __init__(self, name, fs): self.name = name self.fs = fs def __enter__(self): return self def __exit__(self, *args, **kwargs): pass def write(self, text): self.fs.contents[self.name] = text def read(self): return self.fs.contents[self.name] class mockvfs(object): def __init__(self): self.contents = {} def read(self, path): return mockfile(path, self).read() def readlines(self, path): # lines need to contain the trailing '\n' to mock the real readlines return [l for l in mockfile(path, self).read().splitlines(True)] def __call__(self, path, mode, atomictemp): return mockfile(path, self) class testsimplekeyvaluefile(unittest.TestCase): def setUp(self): self.vfs = mockvfs() def testbasicwritingiandreading(self): dw = {b'key1': b'value1', b'Key2': b'value2'} scmutil.simplekeyvaluefile(self.vfs, b'kvfile').write(dw) self.assertEqual(sorted(self.vfs.read(b'kvfile').split(b'\n')), [b'', b'Key2=value2', b'key1=value1']) dr = scmutil.simplekeyvaluefile(self.vfs, b'kvfile').read() self.assertEqual(dr, dw) if not getattr(unittest.TestCase, 'assertRaisesRegex', False): # Python 3.7 deprecates the regex*p* version, but 2.7 lacks # the regex version. assertRaisesRegex = (# camelcase-required unittest.TestCase.assertRaisesRegexp) def testinvalidkeys(self): d = {b'0key1': b'value1', b'Key2': b'value2'} with self.assertRaisesRegex(error.ProgrammingError, 'keys must start with a letter.*'): scmutil.simplekeyvaluefile(self.vfs, b'kvfile').write(d) d = {b'key1@': b'value1', b'Key2': b'value2'} with self.assertRaisesRegex(error.ProgrammingError, 'invalid key.*'): scmutil.simplekeyvaluefile(self.vfs, b'kvfile').write(d) def testinvalidvalues(self): d = {b'key1': b'value1', b'Key2': b'value2\n'} with self.assertRaisesRegex(error.ProgrammingError, 'invalid val.*'): scmutil.simplekeyvaluefile(self.vfs, b'kvfile').write(d) def testcorruptedfile(self): self.vfs.contents[b'badfile'] = b'ababagalamaga\n' with self.assertRaisesRegex(error.CorruptedState, 'dictionary.*element.*'): scmutil.simplekeyvaluefile(self.vfs, b'badfile').read() def testfirstline(self): dw = {b'key1': b'value1'} scmutil.simplekeyvaluefile(self.vfs, b'fl').write(dw, firstline=b'1.0') self.assertEqual(self.vfs.read(b'fl'), b'1.0\nkey1=value1\n') dr = scmutil.simplekeyvaluefile(self.vfs, b'fl')\ .read(firstlinenonkeyval=True) self.assertEqual(dr, {b'__firstline': b'1.0', b'key1': b'value1'}) if __name__ == "__main__": silenttestrunner.main(__name__)