view tests/test-minifileset.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 os
import sys

# make it runnable directly without run-tests.py
sys.path[0:0] = [os.path.join(os.path.dirname(__file__), '..')]

from mercurial import minifileset

def check(text, truecases, falsecases):
    f = minifileset.compile(text)
    for args in truecases:
        if not f(*args):
            print('unexpected: %r should include %r' % (text, args))
    for args in falsecases:
        if f(*args):
            print('unexpected: %r should exclude %r' % (text, args))

check(b'all()', [(b'a.php', 123), (b'b.txt', 0)], [])
check(b'none()', [], [(b'a.php', 123), (b'b.txt', 0)])
check(b'!!!!((!(!!all())))', [], [(b'a.php', 123), (b'b.txt', 0)])

check(b'"path:a" & (**.b | **.c)',
      [(b'a/b.b', 0), (b'a/c.c', 0)], [(b'b/c.c', 0)])
check(b'(path:a & **.b) | **.c',
      [(b'a/b.b', 0), (b'a/c.c', 0), (b'b/c.c', 0)], [])

check(b'**.bin - size("<20B")',
      [(b'b.bin', 21)], [(b'a.bin', 11), (b'b.txt', 21)])

check(b'!!**.bin or size(">20B") + "path:bin" or !size(">10")',
      [(b'a.bin', 11), (b'b.txt', 21), (b'bin/abc', 11)],
      [(b'a.notbin', 11), (b'b.txt', 11), (b'bin2/abc', 11)])

check(
    b'(**.php and size(">10KB")) | **.zip | ("path:bin" & !"path:bin/README") '
    b' | size(">1M")',
    [(b'a.php', 15000), (b'a.zip', 0), (b'bin/a', 0), (b'bin/README', 1e7)],
    [(b'a.php', 5000), (b'b.zip2', 0), (b't/bin/a', 0), (b'bin/README', 1)])