view tests/test-sshserver.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, print_function

import io
import unittest

import silenttestrunner

from mercurial import (
    wireprotoserver,
    wireprotov1server,
)

from mercurial.utils import (
    procutil,
)

class SSHServerGetArgsTests(unittest.TestCase):
    def testparseknown(self):
        tests = [
            (b'* 0\nnodes 0\n', [b'', {}]),
            (b'* 0\nnodes 40\n1111111111111111111111111111111111111111\n',
             [b'1111111111111111111111111111111111111111', {}]),
        ]
        for input, expected in tests:
            self.assertparse(b'known', input, expected)

    def assertparse(self, cmd, input, expected):
        server = mockserver(input)
        proto = wireprotoserver.sshv1protocolhandler(server._ui,
                                                     server._fin,
                                                     server._fout)
        _func, spec = wireprotov1server.commands[cmd]
        self.assertEqual(proto.getargs(spec), expected)

def mockserver(inbytes):
    ui = mockui(inbytes)
    repo = mockrepo(ui)
    return wireprotoserver.sshserver(ui, repo)

class mockrepo(object):
    def __init__(self, ui):
        self.ui = ui

class mockui(object):
    def __init__(self, inbytes):
        self.fin = io.BytesIO(inbytes)
        self.fout = io.BytesIO()
        self.ferr = io.BytesIO()

if __name__ == '__main__':
    # Don't call into msvcrt to set BytesIO to binary mode
    procutil.setbinary = lambda fp: True
    silenttestrunner.main(__name__)