mercurial/fancyopts.py

revlog: add option to mmap revlog index

Following on from Jun Wu's patch last October[1], we have found that using mmap
for the revlog index in repos with large revlogs gives a noticable performance
improvment (~110ms on each hg invocation), particularly for commands that don't
touch the index very much.

This changeset adds this as an option, activated by a new experimental config
option so that it can be enabled on a per-repo basis. The configuration option
specifies an index size threshold at which Mercurial will switch to using mmap
to access the index.

If the configuration option is not specified, the default remains to load the
full file, which seems to be the best option for smaller repos.

Some initial performance numbers for average of 5 invocations of `hg log -l 5`
for different cache states:

| Repo: | HG | FB |
|---|---|---|
| Index size: | 2.3MB | much bigger |
| read (warm): | 237ms | 432ms |
| mmap (warm): | 227ms | 321ms |
|   | (-3%) | (-26%) |
| read (cold): | 397ms | 696ms |
| mmap (cold): | 410ms | 888ms |
|   | (+3%) | (+28%) |

[1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2016-October/088737.html

Test Plan:
`hg log --config experimental.mmapindex=true`

Differential Revision: https://phab.mercurial-scm.org/D477

# fancyopts.py - better command line parsing
#
#  Copyright 2005-2009 Matt Mackall <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

from .i18n import _
from . import (
    error,
    pycompat,
)

# Set of flags to not apply boolean negation logic on
nevernegate = {
    # avoid --no-noninteractive
    'noninteractive',
    # These two flags are special because they cause hg to do one
    # thing and then exit, and so aren't suitable for use in things
    # like aliases anyway.
    'help',
    'version',
}

def gnugetopt(args, options, longoptions):
    """Parse options mostly like getopt.gnu_getopt.

    This is different from getopt.gnu_getopt in that an argument of - will
    become an argument of - instead of vanishing completely.
    """
    extraargs = []
    if '--' in args:
        stopindex = args.index('--')
        extraargs = args[stopindex + 1:]
        args = args[:stopindex]
    opts, parseargs = pycompat.getoptb(args, options, longoptions)
    args = []
    while parseargs:
        arg = parseargs.pop(0)
        if arg and arg[0:1] == '-' and len(arg) > 1:
            parseargs.insert(0, arg)
            topts, newparseargs = pycompat.getoptb(parseargs,\
                                            options, longoptions)
            opts = opts + topts
            parseargs = newparseargs
        else:
            args.append(arg)
    args.extend(extraargs)
    return opts, args


def fancyopts(args, options, state, gnu=False):
    """
    read args, parse options, and store options in state

    each option is a tuple of:

      short option or ''
      long option
      default value
      description
      option value label(optional)

    option types include:

      boolean or none - option sets variable in state to true
      string - parameter string is stored in state
      list - parameter string is added to a list
      integer - parameter strings is stored as int
      function - call function with parameter

    non-option args are returned
    """
    namelist = []
    shortlist = ''
    argmap = {}
    defmap = {}
    negations = {}
    alllong = set(o[1] for o in options)

    for option in options:
        if len(option) == 5:
            short, name, default, comment, dummy = option
        else:
            short, name, default, comment = option
        # convert opts to getopt format
        oname = name
        name = name.replace('-', '_')

        argmap['-' + short] = argmap['--' + oname] = name
        defmap[name] = default

        # copy defaults to state
        if isinstance(default, list):
            state[name] = default[:]
        elif callable(default):
            state[name] = None
        else:
            state[name] = default

        # does it take a parameter?
        if not (default is None or default is True or default is False):
            if short:
                short += ':'
            if oname:
                oname += '='
        elif oname not in nevernegate:
            if oname.startswith('no-'):
                insert = oname[3:]
            else:
                insert = 'no-' + oname
            # backout (as a practical example) has both --commit and
            # --no-commit options, so we don't want to allow the
            # negations of those flags.
            if insert not in alllong:
                assert ('--' + oname) not in negations
                negations['--' + insert] = '--' + oname
                namelist.append(insert)
        if short:
            shortlist += short
        if name:
            namelist.append(oname)

    # parse arguments
    if gnu:
        parse = gnugetopt
    else:
        parse = pycompat.getoptb
    opts, args = parse(args, shortlist, namelist)

    # transfer result to state
    for opt, val in opts:
        boolval = True
        negation = negations.get(opt, False)
        if negation:
            opt = negation
            boolval = False
        name = argmap[opt]
        obj = defmap[name]
        t = type(obj)
        if callable(obj):
            state[name] = defmap[name](val)
        elif t is type(1):
            try:
                state[name] = int(val)
            except ValueError:
                raise error.Abort(_('invalid value %r for option %s, '
                                   'expected int') % (val, opt))
        elif t is type(''):
            state[name] = val
        elif t is type([]):
            state[name].append(val)
        elif t is type(None) or t is type(False):
            state[name] = boolval

    # return unparsed args
    return args