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8 <title>GLEP 61 -- Manifest2 compression</title>
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20 [<b><a href="http://www.gentoo.org/proj/en/glep/glep-0061.txt">GLEP Source</a></b>]
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22 <table class="rfc2822 docutils field-list" frame="void" rules="none">
23 <col class="field-name" />
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25 <tbody valign="top">
26 <tr class="field"><th class="field-name">GLEP:</th><td class="field-body">61</td>
27 </tr>
28 <tr class="field"><th class="field-name">Title:</th><td class="field-body">Manifest2 compression</td>
29 </tr>
30 <tr class="field"><th class="field-name">Version:</th><td class="field-body">1.6</td>
31 </tr>
32 <tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference external" href="http://www.gentoo.org/cgi-bin/viewcvs.cgi/xml/htdocs/proj/en/glep/glep-0061.txt?cvsroot=gentoo">2010/01/31 09:55:43</a></td>
33 </tr>
34 <tr class="field"><th class="field-name">Author:</th><td class="field-body">Robin Hugh Johnson &lt;robbat2&#32;&#97;t&#32;gentoo.org&gt;</td>
35 </tr>
36 <tr class="field"><th class="field-name">Status:</th><td class="field-body">Draft</td>
37 </tr>
38 <tr class="field"><th class="field-name">Type:</th><td class="field-body">Standards Track</td>
39 </tr>
40 <tr class="field"><th class="field-name">Content-Type:</th><td class="field-body"><a class="reference external" href="glep-0002.html">text/x-rst</a></td>
41 </tr>
42 <tr class="field"><th class="field-name">Requires:</th><td class="field-body"><a class="reference external" href="http://www.gentoo.org/proj/en/glepglep-0044.html">44</a></td>
43 </tr>
44 <tr class="field"><th class="field-name">Created:</th><td class="field-body">July 2008</td>
45 </tr>
46 <tr class="field"><th class="field-name">Updated:</th><td class="field-body">October 2008, January 2010</td>
47 </tr>
48 <tr class="field"><th class="field-name">Updates:</th><td class="field-body">44</td>
49 </tr>
50 <tr class="field"><th class="field-name">Post-History:</th><td class="field-body">December 2009, January 2010</td>
51 </tr>
52 </tbody>
53 </table>
54 <hr />
55 <div class="contents topic" id="contents">
56 <p class="topic-title first">Contents</p>
57 <ul class="simple">
58 <li><a class="reference internal" href="#abstract" id="id1">Abstract</a></li>
59 <li><a class="reference internal" href="#motivation" id="id2">Motivation</a></li>
60 <li><a class="reference internal" href="#specification" id="id3">Specification</a><ul>
61 <li><a class="reference internal" href="#creation-of-compressed-manifests" id="id4">Creation of compressed Manifests:</a></li>
62 <li><a class="reference internal" href="#validation-of-manifests" id="id5">Validation of Manifests:</a></li>
63 </ul>
64 </li>
65 <li><a class="reference internal" href="#example-results-with-a-32kib-cut-off-gzip-algorithm" id="id6">Example Results with a 32KiB cut-off, gzip algorithm</a></li>
66 <li><a class="reference internal" href="#backwards-compatibility" id="id7">Backwards Compatibility</a></li>
67 <li><a class="reference internal" href="#references" id="id8">References</a></li>
68 <li><a class="reference internal" href="#copyright" id="id9">Copyright</a></li>
69 </ul>
70 </div>
71 <div class="section" id="abstract">
72 <h1><a class="toc-backref" href="#id1">Abstract</a></h1>
73 <p>Deals with compression of large Manifest2 files.</p>
74 </div>
75 <div class="section" id="motivation">
76 <h1><a class="toc-backref" href="#id2">Motivation</a></h1>
77 <p>With the introduction of MetaManifest, and full-tree Manifest coverage,
78 we are faced with the possibility of having very large Manifests.</p>
79 <p>Preliminary experiments with MetaManifest, show that with just the
80 existing per-package Manifests, the full MetaManifest (top-level only,
81 no first-level sub directories), for a tree including metadata/, exceeds
82 8MiB in size. Applying common compression can achieve a 50-60% reduction
83 in this size.</p>
84 <p>Additionally, some of the larger already-existing Manifests in the tree
85 can also be reduced.</p>
86 <p>This GLEP is not mandatory for the tree-signing specification, but
87 instead helps to cut down the size impact of large Manifest2 files, some
88 of which are already present in the tree. As such, it is also able to
89 stand on it's own.</p>
90 </div>
91 <div class="section" id="specification">
92 <h1><a class="toc-backref" href="#id3">Specification</a></h1>
93 <div class="section" id="creation-of-compressed-manifests">
94 <h2><a class="toc-backref" href="#id4">Creation of compressed Manifests:</a></h2>
95 <p>32KiB is suggested as a arbitrary cut-off point to start generating
96 compressed Manifest2 files.</p>
97 <p>The compression must only applied during the creation of a tree intended
98 for end users. No Manifests stored in a VCS should be compressed in the
99 VCS. For the main gentoo-portage tree, this means that the compressed
100 Manifests should be generated using the CVS to Rsync process.</p>
101 <p>The Manifest compression process is required to ensure that inconsistent
102 compressed versions do not exist.</p>
103 </div>
104 <div class="section" id="validation-of-manifests">
105 <h2><a class="toc-backref" href="#id5">Validation of Manifests:</a></h2>
106 <p>When searching for a Manifest2 file, if the basename form does not
107 exist, the package manager should search in the same location using
108 common compressed suffixes, and use the compressed file in place of the
109 Manifest2.</p>
110 <p>gzip, bzip2, lzma, xz should all be supported if available on the given
111 platform. In the case that multiple versions exist, the package manager
112 should simply pick one - they should be identical, differing only in
113 compression.</p>
114 </div>
115 </div>
116 <div class="section" id="example-results-with-a-32kib-cut-off-gzip-algorithm">
117 <h1><a class="toc-backref" href="#id6">Example Results with a 32KiB cut-off, gzip algorithm</a></h1>
118 <p>As of 2010/01/30, the suggested cut-off would impact the following 21 existing
119 Manifests, for a saving of nearly 900KiB:</p>
120 <pre class="literal-block">
121 Size Path
122 65788 app-doc/linux-gazette/Manifest
123 75739 app-office/openoffice-bin/Manifest
124 40534 app-text/texlive-core/Manifest
125 41710 dev-texlive/texlive-bibtexextra/Manifest
126 38197 dev-texlive/texlive-documentation-english/Manifest
127 129610 dev-texlive/texlive-fontsextra/Manifest
128 36022 dev-texlive/texlive-humanities/Manifest
129 686118 dev-texlive/texlive-latexextra/Manifest
130 43392 dev-texlive/texlive-latexrecommended/Manifest
131 33375 dev-texlive/texlive-mathextra/Manifest
132 39781 dev-texlive/texlive-pictures/Manifest
133 69567 dev-texlive/texlive-pstricks/Manifest
134 75460 dev-texlive/texlive-publishers/Manifest
135 50879 dev-texlive/texlive-science/Manifest
136 36711 kde-base/kde-l10n/Manifest
137 36539 media-gfx/bootsplash-themes/Manifest
138 33058 net-fs/autofs/Manifest
139 39781 www-client/firefox-bin/Manifest
140 48983 www-client/icecat/Manifest
141 60213 www-client/mozilla-firefox/Manifest
142 39065 x11-themes/gkrellm-themes/Manifest
143 </pre>
144 <p>Additionally, with the MetaManifest proposal, the following new manifests would
145 also be compressed, for a saving of nearly 4MiB:</p>
146 <pre class="literal-block">
147 Size Path
148 33442 app-admin/Manifest
149 71073 app-dicts/Manifest
150 35923 app-emacs/Manifest
151 45808 app-misc/Manifest
152 50169 app-text/Manifest
153 112786 dev-java/Manifest
154 65581 dev-libs/Manifest
155 42619 dev-lisp/Manifest
156 182163 dev-perl/Manifest
157 96198 dev-python/Manifest
158 58963 dev-ruby/Manifest
159 59736 dev-util/Manifest
160 58338 eclass/Manifest
161 55749 kde-base/Manifest
162 110064 licenses/Manifest
163 35262 media-gfx/Manifest
164 53995 media-libs/Manifest
165 55607 media-plugins/Manifest
166 71911 media-sound/Manifest
167 34835 media-video/Manifest
168 5747849 metadata/Manifest
169 47452 net-analyzer/Manifest
170 65989 net-misc/Manifest
171 316787 profiles/Manifest
172 67784 sys-apps/Manifest
173 48971 x11-misc/Manifest
174 41475 x11-plugins/Manifest
175 </pre>
176 </div>
177 <div class="section" id="backwards-compatibility">
178 <h1><a class="toc-backref" href="#id7">Backwards Compatibility</a></h1>
179 <p>The package Manifests should also be maintained as ONLY uncompressed in
180 CVS.</p>
181 <p>For processing of all existing per-package Manifests, if compression is
182 used, it should be done in parallel to the existing Manifests, to
183 provide for a changeover period. Newer versions of Portage may later
184 choose to exclude all non-compressed Manifests during emerge --sync if
185 compressed versions are guaranteed to exist on the servers.</p>
186 <p>MetaManifests may come into existence as compressed from the start, as
187 do not have an backwards compatibility issues.</p>
188 <p>As a side note, this breaks all manual interaction with Manifests
189 such as grep, and so should only be applied to large Manifest2 files,
190 such as the MetaManifest.</p>
191 </div>
192 <div class="section" id="references">
193 <h1><a class="toc-backref" href="#id8">References</a></h1>
194 <table class="docutils footnote" frame="void" id="glep44" rules="none">
195 <colgroup><col class="label" /><col /></colgroup>
196 <tbody valign="top">
197 <tr><td class="label">[1]</td><td>Mauch, M. (2005) GLEP44 - Manifest2 format.
198 <a class="reference external" href="http://www.gentoo.org/proj/en/glep/glep-0044.html">http://www.gentoo.org/proj/en/glep/glep-0044.html</a></td></tr>
199 </tbody>
200 </table>
201 </div>
202 <div class="section" id="copyright">
203 <h1><a class="toc-backref" href="#id9">Copyright</a></h1>
204 <p>Copyright (c) 2008-2010 by Robin Hugh Johnson. This material may be
205 distributed only subject to the terms and conditions set forth in the
206 Open Publication License, v1.0.</p>
207 <p>vim: tw=72 ts=2 expandtab:</p>
208 </div>
209
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