Mercurial > hg
view tests/test-imports-checker.t @ 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 | bc2535238de2 |
children | 5abc47d4ca6b |
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#require test-repo $ . "$TESTDIR/helpers-testrepo.sh" $ testrepohgenv $ import_checker="$TESTDIR"/../contrib/import-checker.py Run the doctests from the import checker, and make sure it's working correctly. $ TERM=dumb $ export TERM $ $PYTHON -m doctest $import_checker Run additional tests for the import checker $ mkdir testpackage $ touch testpackage/__init__.py $ cat > testpackage/multiple.py << EOF > from __future__ import absolute_import > import os, sys > EOF $ cat > testpackage/unsorted.py << EOF > from __future__ import absolute_import > import sys > import os > EOF $ cat > testpackage/stdafterlocal.py << EOF > from __future__ import absolute_import > from . import unsorted > import os > EOF $ cat > testpackage/requirerelative.py << EOF > from __future__ import absolute_import > import testpackage.unsorted > EOF $ cat > testpackage/importalias.py << EOF > from __future__ import absolute_import > import ui > EOF $ cat > testpackage/relativestdlib.py << EOF > from __future__ import absolute_import > from .. import os > EOF $ cat > testpackage/symbolimport.py << EOF > from __future__ import absolute_import > from .unsorted import foo > EOF $ cat > testpackage/latesymbolimport.py << EOF > from __future__ import absolute_import > from . import unsorted > from mercurial.node import hex > EOF $ cat > testpackage/multiplegroups.py << EOF > from __future__ import absolute_import > from . import unsorted > from . import more > EOF $ mkdir testpackage/subpackage $ cat > testpackage/subpackage/levelpriority.py << EOF > from __future__ import absolute_import > from . import foo > from .. import parent > EOF $ touch testpackage/subpackage/foo.py $ cat > testpackage/subpackage/__init__.py << EOF > from __future__ import absolute_import > from . import levelpriority # should not cause cycle > EOF $ cat > testpackage/subpackage/localimport.py << EOF > from __future__ import absolute_import > from . import foo > def bar(): > # should not cause "higher-level import should come first" > from .. import unsorted > # but other errors should be detected > from .. import more > import testpackage.subpackage.levelpriority > EOF $ cat > testpackage/importmodulefromsub.py << EOF > from __future__ import absolute_import > from .subpackage import foo # not a "direct symbol import" > EOF $ cat > testpackage/importsymbolfromsub.py << EOF > from __future__ import absolute_import > from .subpackage import foo, nonmodule > EOF $ cat > testpackage/sortedentries.py << EOF > from __future__ import absolute_import > from . import ( > foo, > bar, > ) > EOF $ cat > testpackage/importfromalias.py << EOF > from __future__ import absolute_import > from . import ui > EOF $ cat > testpackage/importfromrelative.py << EOF > from __future__ import absolute_import > from testpackage.unsorted import foo > EOF $ mkdir testpackage2 $ touch testpackage2/__init__.py $ cat > testpackage2/latesymbolimport.py << EOF > from __future__ import absolute_import > from testpackage import unsorted > from mercurial.node import hex > EOF # Shadowing a stdlib module to test "relative import of stdlib module" is # allowed if the module is also being checked $ mkdir email $ touch email/__init__.py $ touch email/errors.py $ cat > email/utils.py << EOF > from __future__ import absolute_import > from . import errors > EOF $ $PYTHON "$import_checker" testpackage*/*.py testpackage/subpackage/*.py \ > email/*.py testpackage/importalias.py:2: ui module must be "as" aliased to uimod testpackage/importfromalias.py:2: ui from testpackage must be "as" aliased to uimod testpackage/importfromrelative.py:2: import should be relative: testpackage.unsorted testpackage/importfromrelative.py:2: direct symbol import foo from testpackage.unsorted testpackage/importsymbolfromsub.py:2: direct symbol import nonmodule from testpackage.subpackage testpackage/latesymbolimport.py:3: symbol import follows non-symbol import: mercurial.node testpackage/multiple.py:2: multiple imported names: os, sys testpackage/multiplegroups.py:3: multiple "from . import" statements testpackage/relativestdlib.py:2: relative import of stdlib module testpackage/requirerelative.py:2: import should be relative: testpackage.unsorted testpackage/sortedentries.py:2: imports from testpackage not lexically sorted: bar < foo testpackage/stdafterlocal.py:3: stdlib import "os" follows local import: testpackage testpackage/subpackage/levelpriority.py:3: higher-level import should come first: testpackage testpackage/subpackage/localimport.py:7: multiple "from .. import" statements testpackage/subpackage/localimport.py:8: import should be relative: testpackage.subpackage.levelpriority testpackage/symbolimport.py:2: direct symbol import foo from testpackage.unsorted testpackage/unsorted.py:3: imports not lexically sorted: os < sys testpackage2/latesymbolimport.py:3: symbol import follows non-symbol import: mercurial.node [1]