view tests/test-check-config.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"

Sanity check check-config.py

  $ cat > testfile.py << EOF
  > # Good
  > foo = ui.config('ui', 'username')
  > # Missing
  > foo = ui.config('ui', 'doesnotexist')
  > # Missing different type
  > foo = ui.configint('ui', 'missingint')
  > # Missing with default value
  > foo = ui.configbool('ui', 'missingbool1', default=True)
  > foo = ui.configbool('ui', 'missingbool2', False)
  > # Inconsistent values for defaults.
  > foo = ui.configint('ui', 'intdefault', default=1)
  > foo = ui.configint('ui', 'intdefault', default=42)
  > # Can suppress inconsistent value error
  > foo = ui.configint('ui', 'intdefault2', default=1)
  > # inconsistent config: ui.intdefault2
  > foo = ui.configint('ui', 'intdefault2', default=42)
  > EOF

  $ cat > files << EOF
  > mercurial/help/config.txt
  > $TESTTMP/testfile.py
  > EOF

  $ cd "$TESTDIR"/..

  $ $PYTHON contrib/check-config.py < $TESTTMP/files
  foo = ui.configint('ui', 'intdefault', default=42)
  conflict on ui.intdefault: ('int', '42') != ('int', '1')
  at $TESTTMP/testfile.py:12:
  undocumented: ui.doesnotexist (str)
  undocumented: ui.intdefault (int) [42]
  undocumented: ui.intdefault2 (int) [42]
  undocumented: ui.missingbool1 (bool) [True]
  undocumented: ui.missingbool2 (bool)
  undocumented: ui.missingint (int)

New errors are not allowed. Warnings are strongly discouraged.

  $ testrepohg files "set:(**.py or **.txt) - tests/**" | sed 's|\\|/|g' |
  >   $PYTHON contrib/check-config.py