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discovery: slowly increase sampling size...
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.

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hg.1.txt
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====
hg
====
---------------------------------------
Mercurial source code management system
---------------------------------------
:Author: Matt Mackall <mpm@selenic.com>
:Organization: Mercurial
:Manual section: 1
:Manual group: Mercurial Manual
.. contents::
:backlinks: top
:class: htmlonly
:depth: 1
Synopsis
""""""""
**hg** *command* [*option*]... [*argument*]...
Description
"""""""""""
The **hg** command provides a command line interface to the Mercurial
system.
Command Elements
""""""""""""""""
files...
indicates one or more filename or relative path filenames; see
`File Name Patterns`_ for information on pattern matching
path
indicates a path on the local machine
revision
indicates a changeset which can be specified as a changeset
revision number, a tag, or a unique substring of the changeset
hash value
repository path
either the pathname of a local repository or the URI of a remote
repository.
.. include:: hg.1.gendoc.txt
Files
"""""
``/etc/mercurial/hgrc``, ``$HOME/.hgrc``, ``.hg/hgrc``
This file contains defaults and configuration. Values in
``.hg/hgrc`` override those in ``$HOME/.hgrc``, and these override
settings made in the global ``/etc/mercurial/hgrc`` configuration.
See |hgrc(5)|_ for details of the contents and format of these
files.
``.hgignore``
This file contains regular expressions (one per line) that
describe file names that should be ignored by **hg**. For details,
see |hgignore(5)|_.
``.hgsub``
This file defines the locations of all subrepositories, and
tells where the subrepository checkouts came from. For details, see
:hg:`help subrepos`.
``.hgsubstate``
This file is where Mercurial stores all nested repository states. *NB: This
file should not be edited manually.*
``.hgtags``
This file contains changeset hash values and text tag names (one
of each separated by spaces) that correspond to tagged versions of
the repository contents. The file content is encoded using UTF-8.
``.hg/last-message.txt``
This file is used by :hg:`commit` to store a backup of the commit message
in case the commit fails.
``.hg/localtags``
This file can be used to define local tags which are not shared among
repositories. The file format is the same as for ``.hgtags``, but it is
encoded using the local system encoding.
Some commands (e.g. revert) produce backup files ending in ``.orig``,
if the ``.orig`` file already exists and is not tracked by Mercurial,
it will be overwritten.
Bugs
""""
Probably lots, please post them to the mailing list (see Resources_
below) when you find them.
See Also
""""""""
|hgignore(5)|_, |hgrc(5)|_
Author
""""""
Written by Matt Mackall <mpm@selenic.com>
Resources
"""""""""
Main Web Site: https://mercurial-scm.org/
Source code repository: https://www.mercurial-scm.org/repo/hg
Mailing list: https://www.mercurial-scm.org/mailman/listinfo/mercurial/
Copying
"""""""
Copyright (C) 2005-2019 Matt Mackall.
Free use of this software is granted under the terms of the GNU General
Public License version 2 or any later version.
.. include:: common.txt