view hgext/record.py @ 42354:dbd0fcca6dfc

discovery: slowly increase sampling size

Some pathological discovery runs can requires many roundtrip. When this happens
things can get very slow.

To make the algorithm more resilience again such pathological case. We slowly
increase the sample size with each roundtrip (+5%). This will have a negligible
impact on "normal" discovery with few roundtrips, but a large positive impact of
case with many roundtrips. Asking more question per roundtrip helps to reduce
the undecided set faster. Instead of reducing the undecided set a linear speed
(in the worst case), we reduce it as a guaranteed (small) exponential rate. The
data below show this slow ramp up in sample size:

round trip    |    1 |     5 |    10 |    20 |     50 |     100 |       130 |
sample size   |  200 |   254 |   321 |   517 |  2 199 |  25 123 |   108 549 |
covered nodes |  200 | 1 357 | 2 821 | 7 031 | 42 658 | 524 530 | 2 276 755 |

To be a bit more concrete, lets take a very pathological case as an example. We
are doing discovery from a copy of Mozilla-try to a more recent version of
mozilla-unified. Mozilla-unified heads are unknown to the mozilla-try repo and
there are over 1 million "missing" changesets. (the discovery is "local" to
avoid network interference)

Without this change, the discovery:
- last 1858 seconds (31 minutes),
- does 1700 round trip,
- asking about 340 000 nodes.

With this change, the discovery:
- last 218 seconds (3 minutes, 38 seconds a -88% improvement),
- does 94 round trip (-94%),
- asking about 344 211 nodes (+1%).

Of course, this is an extreme case (and 3 minutes is still slow). However this
give a good example of how this sample size increase act as a safety net
catching any bad situations.

We could image a steeper increase than 5%. For example 10% would give the
following number:

round trip    |    1 |     5 |    10 |     20 |     50  |        75 |        100 |
sample size   |  200 |   321 |   514 |  1 326 |  23 060 |   249 812 |  2 706 594 |
covered nodes |  200 | 1 541 | 3 690 | 12 671 | 251 871 | 2 746 254 | 29 770 966 |

In parallel, it is useful to understand these pathological cases and improve
them. However the current change provides a general purpose safety net to smooth
the impact of pathological cases.

To avoid issue with older http server, the increase in sample size only occurs
if the protocol has not limit on command argument size.

# record.py
#
# Copyright 2007 Bryan O'Sullivan <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

'''commands to interactively select changes for commit/qrefresh (DEPRECATED)

The feature provided by this extension has been moved into core Mercurial as
:hg:`commit --interactive`.'''

from __future__ import absolute_import

from mercurial.i18n import _
from mercurial import (
    cmdutil,
    commands,
    error,
    extensions,
    registrar,
)

cmdtable = {}
command = registrar.command(cmdtable)
# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'


@command("record",
         # same options as commit + white space diff options
        [c for c in commands.table['commit|ci'][1][:]
            if c[1] != "interactive"] + cmdutil.diffwsopts,
          _('hg record [OPTION]... [FILE]...'),
        helpcategory=command.CATEGORY_COMMITTING)
def record(ui, repo, *pats, **opts):
    '''interactively select changes to commit

    If a list of files is omitted, all changes reported by :hg:`status`
    will be candidates for recording.

    See :hg:`help dates` for a list of formats valid for -d/--date.

    If using the text interface (see :hg:`help config`),
    you will be prompted for whether to record changes to each
    modified file, and for files with multiple changes, for each
    change to use. For each query, the following responses are
    possible::

      y - record this change
      n - skip this change
      e - edit this change manually

      s - skip remaining changes to this file
      f - record remaining changes to this file

      d - done, skip remaining changes and files
      a - record all changes to all remaining files
      q - quit, recording no changes

      ? - display help

    This command is not available when committing a merge.'''

    if not ui.interactive():
        raise error.Abort(_('running non-interactively, use %s instead') %
                         'commit')

    opts[r"interactive"] = True
    overrides = {('experimental', 'crecord'): False}
    with ui.configoverride(overrides, 'record'):
        return commands.commit(ui, repo, *pats, **opts)

def qrefresh(origfn, ui, repo, *pats, **opts):
    if not opts[r'interactive']:
        return origfn(ui, repo, *pats, **opts)

    mq = extensions.find('mq')

    def committomq(ui, repo, *pats, **opts):
        # At this point the working copy contains only changes that
        # were accepted. All other changes were reverted.
        # We can't pass *pats here since qrefresh will undo all other
        # changed files in the patch that aren't in pats.
        mq.refresh(ui, repo, **opts)

    # backup all changed files
    cmdutil.dorecord(ui, repo, committomq, None, True,
                    cmdutil.recordfilter, *pats, **opts)

# This command registration is replaced during uisetup().
@command('qrecord',
    [],
    _('hg qrecord [OPTION]... PATCH [FILE]...'),
    helpcategory=command.CATEGORY_COMMITTING,
    inferrepo=True)
def qrecord(ui, repo, patch, *pats, **opts):
    '''interactively record a new patch

    See :hg:`help qnew` & :hg:`help record` for more information and
    usage.
    '''
    return _qrecord('qnew', ui, repo, patch, *pats, **opts)

def _qrecord(cmdsuggest, ui, repo, patch, *pats, **opts):
    try:
        mq = extensions.find('mq')
    except KeyError:
        raise error.Abort(_("'mq' extension not loaded"))

    repo.mq.checkpatchname(patch)

    def committomq(ui, repo, *pats, **opts):
        opts[r'checkname'] = False
        mq.new(ui, repo, patch, *pats, **opts)

    overrides = {('experimental', 'crecord'): False}
    with ui.configoverride(overrides, 'record'):
        cmdutil.checkunfinished(repo)
        cmdutil.dorecord(ui, repo, committomq, cmdsuggest, False,
                         cmdutil.recordfilter, *pats, **opts)

def qnew(origfn, ui, repo, patch, *args, **opts):
    if opts[r'interactive']:
        return _qrecord(None, ui, repo, patch, *args, **opts)
    return origfn(ui, repo, patch, *args, **opts)


def uisetup(ui):
    try:
        mq = extensions.find('mq')
    except KeyError:
        return

    cmdtable["qrecord"] = (
        qrecord,
        # same options as qnew, but copy them so we don't get
        # -i/--interactive for qrecord and add white space diff options
        mq.cmdtable['qnew'][1][:] + cmdutil.diffwsopts,
        _('hg qrecord [OPTION]... PATCH [FILE]...'))

    _wrapcmd('qnew', mq.cmdtable, qnew, _("interactively record a new patch"))
    _wrapcmd('qrefresh', mq.cmdtable, qrefresh,
             _("interactively select changes to refresh"))

def _wrapcmd(cmd, table, wrapfn, msg):
    entry = extensions.wrapcommand(table, cmd, wrapfn)
    entry[1].append(('i', 'interactive', None, msg))