view tests/test-annotate.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

from __future__ import absolute_import
from __future__ import print_function

import unittest

from mercurial import (
    mdiff,
    pycompat,
)
from mercurial.dagop import (
    annotateline,
    _annotatedfile,
    _annotatepair,
)

def tr(a):
    return [annotateline(fctx, lineno, skip)
            for fctx, lineno, skip in zip(a.fctxs, a.linenos, a.skips)]

class AnnotateTests(unittest.TestCase):
    """Unit tests for annotate code."""

    def testannotatepair(self):
        self.maxDiff = None # camelcase-required

        oldfctx = b'old'
        p1fctx, p2fctx, childfctx = b'p1', b'p2', b'c'
        olddata = b'a\nb\n'
        p1data = b'a\nb\nc\n'
        p2data = b'a\nc\nd\n'
        childdata = b'a\nb2\nc\nc2\nd\n'
        diffopts = mdiff.diffopts()

        def decorate(text, fctx):
            n = text.count(b'\n')
            linenos = pycompat.rangelist(1, n + 1)
            return _annotatedfile([fctx] * n, linenos, [False] * n, text)

        # Basic usage

        oldann = decorate(olddata, oldfctx)
        p1ann = decorate(p1data, p1fctx)
        p1ann = _annotatepair([oldann], p1fctx, p1ann, False, diffopts)
        self.assertEqual(tr(p1ann), [
            annotateline(b'old', 1),
            annotateline(b'old', 2),
            annotateline(b'p1', 3),
        ])

        p2ann = decorate(p2data, p2fctx)
        p2ann = _annotatepair([oldann], p2fctx, p2ann, False, diffopts)
        self.assertEqual(tr(p2ann), [
            annotateline(b'old', 1),
            annotateline(b'p2', 2),
            annotateline(b'p2', 3),
        ])

        # Test with multiple parents (note the difference caused by ordering)

        childann = decorate(childdata, childfctx)
        childann = _annotatepair([p1ann, p2ann], childfctx, childann, False,
                                 diffopts)
        self.assertEqual(tr(childann), [
            annotateline(b'old', 1),
            annotateline(b'c', 2),
            annotateline(b'p2', 2),
            annotateline(b'c', 4),
            annotateline(b'p2', 3),
        ])

        childann = decorate(childdata, childfctx)
        childann = _annotatepair([p2ann, p1ann], childfctx, childann, False,
                                 diffopts)
        self.assertEqual(tr(childann), [
            annotateline(b'old', 1),
            annotateline(b'c', 2),
            annotateline(b'p1', 3),
            annotateline(b'c', 4),
            annotateline(b'p2', 3),
        ])

        # Test with skipchild (note the difference caused by ordering)

        childann = decorate(childdata, childfctx)
        childann = _annotatepair([p1ann, p2ann], childfctx, childann, True,
                                 diffopts)
        self.assertEqual(tr(childann), [
            annotateline(b'old', 1),
            annotateline(b'old', 2, True),
            # note that this line was carried over from earlier so it is *not*
            # marked skipped
            annotateline(b'p2', 2),
            annotateline(b'p2', 2, True),
            annotateline(b'p2', 3),
        ])

        childann = decorate(childdata, childfctx)
        childann = _annotatepair([p2ann, p1ann], childfctx, childann, True,
                                 diffopts)
        self.assertEqual(tr(childann), [
            annotateline(b'old', 1),
            annotateline(b'old', 2, True),
            annotateline(b'p1', 3),
            annotateline(b'p1', 3, True),
            annotateline(b'p2', 3),
        ])

if __name__ == '__main__':
    import silenttestrunner
    silenttestrunner.main(__name__)