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11/* 11/*
12:Author: David Goodger 12:Author: David Goodger
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14:date: $Date: 2009/05/17 17:00:30 $ 14:date: $Date: 2009/05/17 20:56:53 $
15:version: $Revision: 1.4 $ 15:version: $Revision: 1.5 $
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268<tbody valign="top"> 268<tbody valign="top">
269<tr class="field"><th class="field-name">GLEP:</th><td class="field-body">55</td> 269<tr class="field"><th class="field-name">GLEP:</th><td class="field-body">55</td>
270</tr> 270</tr>
271<tr class="field"><th class="field-name">Title:</th><td class="field-body">Use EAPI-suffixed ebuilds (.ebuild-EAPI)</td> 271<tr class="field"><th class="field-name">Title:</th><td class="field-body">Use EAPI-suffixed ebuilds (.ebuild-EAPI)</td>
272</tr> 272</tr>
273<tr class="field"><th class="field-name">Version:</th><td class="field-body">1.3</td> 273<tr class="field"><th class="field-name">Version:</th><td class="field-body">1.4</td>
274</tr> 274</tr>
275<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-0055.txt?cvsroot=gentoo">2009/05/17 15:50:27</a></td> 275<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-0055.txt?cvsroot=gentoo">2009/05/17 17:00:30</a></td>
276</tr> 276</tr>
277<tr class="field"><th class="field-name">Author:</th><td class="field-body">Piotr Jaroszyński &lt;peper&#32;&#97;t&#32;gentoo.org&gt;</td> 277<tr class="field"><th class="field-name">Author:</th><td class="field-body">Piotr Jaroszyński &lt;peper&#32;&#97;t&#32;gentoo.org&gt;</td>
278</tr> 278</tr>
279<tr class="field"><th class="field-name">Status:</th><td class="field-body">Draft</td> 279<tr class="field"><th class="field-name">Status:</th><td class="field-body">Draft</td>
280</tr> 280</tr>
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516allowing authors to provide backwards compatible ebuilds, it would introduce 516allowing authors to provide backwards compatible ebuilds, it would introduce
517problems too. The first is the requirement to have strict EAPI ordering, the 517problems too. The first is the requirement to have strict EAPI ordering, the
518second is ensuring that all the ebuilds for a single category/package-version 518second is ensuring that all the ebuilds for a single category/package-version
519are equivalent, i.e. installing any of them has exactly the same effect on a 519are equivalent, i.e. installing any of them has exactly the same effect on a
520given system.</p> 520given system.</p>
521<p>Also note that it is not a new restriction. It is already possible to illegally
522have multiple versions with different EAPIs as e.g. <tt class="docutils literal"><span class="pre">1.0</span> <span class="pre">==</span> <span class="pre">1.00</span> <span class="pre">==</span> <span class="pre">1.00-r0</span></tt>
523and hence you could have <tt class="docutils literal"><span class="pre">foo-1.0.ebuild</span></tt> with EAPI X and <tt class="docutils literal"><span class="pre">foo-1.00.ebuild</span></tt>
524with EAPI Y.</p>
521</div> 525</div>
522<div class="section" id="summary-of-ideas"> 526<div class="section" id="summary-of-ideas">
523<h1><a class="toc-backref" href="#id13">Summary of ideas</a></h1> 527<h1><a class="toc-backref" href="#id13">Summary of ideas</a></h1>
524<div class="section" id="eapi-suffixed-ebuilds-proposed-solution"> 528<div class="section" id="eapi-suffixed-ebuilds-proposed-solution">
525<h2><a class="toc-backref" href="#id14">EAPI-suffixed ebuilds (proposed solution)</a></h2> 529<h2><a class="toc-backref" href="#id14">EAPI-suffixed ebuilds (proposed solution)</a></h2>
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562behaviour section for old package managers.</p> 566behaviour section for old package managers.</p>
563<p>Performance decrease comes from the fact that with version format changes in the 567<p>Performance decrease comes from the fact that with version format changes in the
564picture package managers need EAPI to parse the ebuild's version. That means that merely 568picture package managers need EAPI to parse the ebuild's version. That means that merely
565picking the best version of a package requires loading EAPI (from cache or the 569picking the best version of a package requires loading EAPI (from cache or the
566ebuild) for each available ebuild.</p> 570ebuild) for each available ebuild.</p>
571<p>Here is more or less how the package manager figures out the best available
572version for a package with N versions available.</p>
573<blockquote>
574<ul class="simple">
575<li>EAPI in the filename<ul>
576<li>Read the directory containing the package - readdir()</li>
577<li>For each ebuild, read its EAPI and using that parse its version - no I/O</li>
578<li>Sort the versions - no I/O</li>
579<li>Going down from the highest to the lowest version<ul>
580<li>Get the metadata from cache - 2 x stat() + read()</li>
581<li>break if the version is visible</li>
582</ul>
583</li>
584</ul>
585</li>
586<li>EAPI in the ebuild<ul>
587<li>Read the directory containing the package - readdir()</li>
588<li>For each ebuild load its metadata from cache to get its EAPI - N x (2 x stat() + read())</li>
589<li>Sort the versions - no I/O</li>
590<li>Going down from the highest to the lowest version<ul>
591<li>(metadata is already loaded) - no I/O</li>
592<li>break if the version is visible - no I/O</li>
593</ul>
594</li>
595</ul>
596</li>
597</ul>
598</blockquote>
599<p>The difference is in for how many versions the package manager needs to hit
600cache. With EAPI in the ebuild it needs to do that for all versions, with EAPI
601in the filename it depends on versions visibility.
602For example, package foo has versions 1, 2, 3, 4, 5 and 6. 6 is masked, 5 is
603~arch and 1,2,3 and 4 are arch. Say, the user accepts only arch for this
604package. With EAPI in the filename it will read metadata only for versions
6056, 5 and 4. With EAPI in the ebuild it needs to load metadata for all versions.</p>
606<p>It's hard to say what's the avarage case, but surely the worst case scenario
607(when only the lowest version is visible) is uncommon.</p>
567</div> 608</div>
568<div class="section" id="easily-fetchable-eapi-inside-the-ebuild-and-one-time-extension-change"> 609<div class="section" id="easily-fetchable-eapi-inside-the-ebuild-and-one-time-extension-change">
569<h2><a class="toc-backref" href="#id17">Easily fetchable EAPI inside the ebuild and one-time extension change</a></h2> 610<h2><a class="toc-backref" href="#id17">Easily fetchable EAPI inside the ebuild and one-time extension change</a></h2>
570<dl class="docutils"> 611<dl class="docutils">
571<dt>Properties:</dt> 612<dt>Properties:</dt>
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619 660
620</div> 661</div>
621<div class="footer"> 662<div class="footer">
622<hr class="footer" /> 663<hr class="footer" />
623<a class="reference external" href="glep-0055.txt">View document source</a>. 664<a class="reference external" href="glep-0055.txt">View document source</a>.
624Generated on: 2009-05-17 16:58 UTC. 665Generated on: 2009-05-17 20:42 UTC.
625Generated by <a class="reference external" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference external" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source. 666Generated by <a class="reference external" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference external" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
626 667
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