view tests/test-check-py3-compat.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

#require test-repo

  $ . "$TESTDIR/helpers-testrepo.sh"
  $ cd "$TESTDIR"/..

  $ testrepohg files 'set:(**.py)' \
  > -X hgdemandimport/demandimportpy2.py \
  > -X mercurial/thirdparty/cbor \
  > | sed 's|\\|/|g' | xargs $PYTHON contrib/check-py3-compat.py
  contrib/python-zstandard/setup.py not using absolute_import
  contrib/python-zstandard/setup_zstd.py not using absolute_import
  contrib/python-zstandard/tests/common.py not using absolute_import
  contrib/python-zstandard/tests/test_buffer_util.py not using absolute_import
  contrib/python-zstandard/tests/test_compressor.py not using absolute_import
  contrib/python-zstandard/tests/test_compressor_fuzzing.py not using absolute_import
  contrib/python-zstandard/tests/test_data_structures.py not using absolute_import
  contrib/python-zstandard/tests/test_data_structures_fuzzing.py not using absolute_import
  contrib/python-zstandard/tests/test_decompressor.py not using absolute_import
  contrib/python-zstandard/tests/test_decompressor_fuzzing.py not using absolute_import
  contrib/python-zstandard/tests/test_estimate_sizes.py not using absolute_import
  contrib/python-zstandard/tests/test_module_attributes.py not using absolute_import
  contrib/python-zstandard/tests/test_train_dictionary.py not using absolute_import
  setup.py not using absolute_import

#if py3exe
  $ testrepohg files 'set:(**.py) - grep(pygments)' \
  > -X hgdemandimport/demandimportpy2.py \
  > -X hgext/fsmonitor/pywatchman \
  > | sed 's|\\|/|g' | xargs $PYTHON3 contrib/check-py3-compat.py \
  > | sed 's/[0-9][0-9]*)$/*)/'
  hgext/convert/transport.py: error importing: <*Error> No module named 'svn.client' (error at transport.py:*) (glob)
  mercurial/cffi/bdiff.py: error importing: <ImportError> cannot import name '_bdiff' (error at bdiff.py:*)
  mercurial/cffi/bdiffbuild.py: error importing: <ImportError> No module named 'cffi' (error at bdiffbuild.py:*)
  mercurial/cffi/mpatch.py: error importing: <ImportError> cannot import name '_mpatch' (error at mpatch.py:*)
  mercurial/cffi/mpatchbuild.py: error importing: <ImportError> No module named 'cffi' (error at mpatchbuild.py:*)
  mercurial/cffi/osutilbuild.py: error importing: <ImportError> No module named 'cffi' (error at osutilbuild.py:*)
  mercurial/scmwindows.py: error importing: <*Error> No module named 'msvcrt' (error at win32.py:*) (glob)
  mercurial/win32.py: error importing: <*Error> No module named 'msvcrt' (error at win32.py:*) (glob)
  mercurial/windows.py: error importing: <*Error> No module named 'msvcrt' (error at windows.py:*) (glob)

#endif

#if py3exe py3pygments
  $ testrepohg files 'set:(**.py) and grep(pygments)' | sed 's|\\|/|g' \
  > | xargs $PYTHON3 contrib/check-py3-compat.py \
  > | sed 's/[0-9][0-9]*)$/*)/'
#endif