view tests/test-ui-verbosity.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 os
from mercurial import (
    pycompat,
    ui as uimod,
)

if pycompat.ispy3:
    xrange = range

hgrc = os.environ['HGRCPATH']
f = open(hgrc)
basehgrc = f.read()
f.close()

print('      hgrc settings    command line options      final result   ')
print('    quiet verbo debug   quiet verbo debug      quiet verbo debug')

for i in xrange(64):
    hgrc_quiet   = bool(i & 1<<0)
    hgrc_verbose = bool(i & 1<<1)
    hgrc_debug   = bool(i & 1<<2)
    cmd_quiet    = bool(i & 1<<3)
    cmd_verbose  = bool(i & 1<<4)
    cmd_debug    = bool(i & 1<<5)

    f = open(hgrc, 'w')
    f.write(basehgrc)
    f.write('\n[ui]\n')
    if hgrc_quiet:
        f.write('quiet = True\n')
    if hgrc_verbose:
        f.write('verbose = True\n')
    if hgrc_debug:
        f.write('debug = True\n')
    f.close()

    u = uimod.ui.load()
    if cmd_quiet or cmd_debug or cmd_verbose:
        u.setconfig(b'ui', b'quiet', pycompat.bytestr(bool(cmd_quiet)))
        u.setconfig(b'ui', b'verbose', pycompat.bytestr(bool(cmd_verbose)))
        u.setconfig(b'ui', b'debug', pycompat.bytestr(bool(cmd_debug)))

    check = ''
    if u.debugflag:
        if not u.verbose or u.quiet:
            check = ' *'
    elif u.verbose and u.quiet:
        check = ' +'

    print(('%2d  %5s %5s %5s   %5s %5s %5s  ->  %5s %5s %5s%s'
           % (i, hgrc_quiet, hgrc_verbose, hgrc_debug,
              cmd_quiet, cmd_verbose, cmd_debug,
              u.quiet, u.verbose, u.debugflag, check)))