Mercurial > hg
view tests/test-hgweb-removed.t @ 34824:e2ad93bcc084
revlog: introduce an experimental flag to slice chunks reads when too sparse
Delta chains can become quite sparse if there is a lot of unrelated data between
relevant pieces. Right now, revlog always reads all the necessary data for the
delta chain in one single read. This can lead to a lot of unrelated data to be
read (see issue5482 for more details).
One can use the `experimental.maxdeltachainspan` option with a large value
(or -1) to easily produce a very sparse delta chain.
This change introduces the ability to slice the chunks retrieval into multiple
reads, skipping large sections of unrelated data. Preliminary testing shows
interesting results. For example the peak memory consumption to read a manifest
on a large repository is reduced from 600MB to 250MB (200MB without
maxdeltachainspan). However, the slicing itself and the multiple reads can have
an negative impact on performance. This is why the new feature is hidden behind
an experimental flag.
Future changesets will add various parameters to control the slicing heuristics.
We hope to experiment a wide variety of repositories during 4.4 and hopefully
turn the feature on by default in 4.5.
As a first try, the algorithm itself is prone to deep changes. However, we wish
to define APIs and have a baseline to work on.
| author | Paul Morelle <paul.morelle@octobus.net> |
|---|---|
| date | Tue, 10 Oct 2017 17:50:27 +0200 |
| parents | cba4461aa0a0 |
| children | 9acc0360ff67 |
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#require serve setting up repo $ hg init test $ cd test $ echo a > a $ hg ci -Ama adding a $ hg rm a $ hg ci -mdel set up hgweb $ hg serve -n test -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log $ cat hg.pid >> $DAEMON_PIDS revision $ get-with-headers.py localhost:$HGPORT 'rev/tip' 200 Script output follows <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-US"> <head> <link rel="icon" href="/static/hgicon.png" type="image/png" /> <meta name="robots" content="index, nofollow" /> <link rel="stylesheet" href="/static/style-paper.css" type="text/css" /> <script type="text/javascript" src="/static/mercurial.js"></script> <title>test: c78f6c5cbea9</title> </head> <body> <div class="container"> <div class="menu"> <div class="logo"> <a href="https://mercurial-scm.org/"> <img src="/static/hglogo.png" alt="mercurial" /></a> </div> <ul> <li><a href="/shortlog/tip">log</a></li> <li><a href="/graph/tip">graph</a></li> <li><a href="/tags">tags</a></li> <li><a href="/bookmarks">bookmarks</a></li> <li><a href="/branches">branches</a></li> </ul> <ul> <li class="active">changeset</li> <li><a href="/raw-rev/tip">raw</a></li> <li><a href="/file/tip">browse</a></li> </ul> <ul> </ul> <ul> <li><a href="/help">help</a></li> </ul> </div> <div class="main"> <h2 class="breadcrumb"><a href="/">Mercurial</a> </h2> <h3> changeset 1:<a href="/rev/c78f6c5cbea9">c78f6c5cbea9</a> <span class="tag">tip</span> </h3> <form class="search" action="/log"> <p><input name="rev" id="search1" type="text" size="30" value="" /></p> <div id="hint">Find changesets by keywords (author, files, the commit message), revision number or hash, or <a href="/help/revsets">revset expression</a>.</div> </form> <div class="description">del</div> <table id="changesetEntry"> <tr> <th class="author">author</th> <td class="author">test</td> </tr> <tr> <th class="date">date</th> <td class="date age">Thu, 01 Jan 1970 00:00:00 +0000</td> </tr> <tr> <th class="author">parents</th> <td class="author"><a href="/rev/cb9a9f314b8b">cb9a9f314b8b</a> </td> </tr> <tr> <th class="author">children</th> <td class="author"></td> </tr> <tr> <th class="files">files</th> <td class="files">a </td> </tr> <tr> <th class="diffstat">diffstat</th> <td class="diffstat"> 1 files changed, 0 insertions(+), 1 deletions(-) <a id="diffstatexpand" href="javascript:toggleDiffstat()">[<tt>+</tt>]</a> <div id="diffstatdetails" style="display:none;"> <a href="javascript:toggleDiffstat()">[<tt>-</tt>]</a> <table class="diffstat-table stripes2"> <tr> <td class="diffstat-file"><a href="#l1.1">a</a></td> <td class="diffstat-total" align="right">1</td> <td class="diffstat-graph"> <span class="diffstat-add" style="width:0.0%;"> </span> <span class="diffstat-remove" style="width:100.0%;"> </span> </td> </tr> </table> </div> </td> </tr> </table> <div class="overflow"> <div class="sourcefirst linewraptoggle">line wrap: <a class="linewraplink" href="javascript:toggleLinewrap()">on</a></div> <div class="sourcefirst"> line diff</div> <div class="stripes2 diffblocks"> <div class="bottomline inc-lineno"><pre class="sourcelines wrap"> <span id="l1.1" class="minusline">--- a/a Thu Jan 01 00:00:00 1970 +0000</span><a href="#l1.1"></a> <span id="l1.2" class="plusline">+++ /dev/null Thu Jan 01 00:00:00 1970 +0000</span><a href="#l1.2"></a> <span id="l1.3" class="atline">@@ -1,1 +0,0 @@</span><a href="#l1.3"></a> <span id="l1.4" class="minusline">-a</span><a href="#l1.4"></a></pre></div> </div> </div> </div> </div> </body> </html> diff removed file $ get-with-headers.py localhost:$HGPORT 'diff/tip/a' 200 Script output follows <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en-US"> <head> <link rel="icon" href="/static/hgicon.png" type="image/png" /> <meta name="robots" content="index, nofollow" /> <link rel="stylesheet" href="/static/style-paper.css" type="text/css" /> <script type="text/javascript" src="/static/mercurial.js"></script> <title>test: a diff</title> </head> <body> <div class="container"> <div class="menu"> <div class="logo"> <a href="https://mercurial-scm.org/"> <img src="/static/hglogo.png" alt="mercurial" /></a> </div> <ul> <li><a href="/shortlog/tip">log</a></li> <li><a href="/graph/tip">graph</a></li> <li><a href="/tags">tags</a></li> <li><a href="/bookmarks">bookmarks</a></li> <li><a href="/branches">branches</a></li> </ul> <ul> <li><a href="/rev/tip">changeset</a></li> <li><a href="/file/tip">browse</a></li> </ul> <ul> <li><a href="/file/tip/a">file</a></li> <li><a href="/file/tip/a">latest</a></li> <li class="active">diff</li> <li><a href="/comparison/tip/a">comparison</a></li> <li><a href="/annotate/tip/a">annotate</a></li> <li><a href="/log/tip/a">file log</a></li> <li><a href="/raw-file/tip/a">raw</a></li> </ul> <ul> <li><a href="/help">help</a></li> </ul> </div> <div class="main"> <h2 class="breadcrumb"><a href="/">Mercurial</a> </h2> <h3> diff a @ 1:<a href="/rev/c78f6c5cbea9">c78f6c5cbea9</a> <span class="tag">tip</span> </h3> <form class="search" action="/log"> <p><input name="rev" id="search1" type="text" size="30" value="" /></p> <div id="hint">Find changesets by keywords (author, files, the commit message), revision number or hash, or <a href="/help/revsets">revset expression</a>.</div> </form> <div class="description">del</div> <table id="changesetEntry"> <tr> <th>author</th> <td>test</td> </tr> <tr> <th>date</th> <td class="date age">Thu, 01 Jan 1970 00:00:00 +0000</td> </tr> <tr> <th>parents</th> <td><a href="/file/cb9a9f314b8b/a">cb9a9f314b8b</a> </td> </tr> <tr> <th>children</th> <td></td> </tr> </table> <div class="overflow"> <div class="sourcefirst linewraptoggle">line wrap: <a class="linewraplink" href="javascript:toggleLinewrap()">on</a></div> <div class="sourcefirst"> line diff</div> <div class="stripes2 diffblocks"> <div class="bottomline inc-lineno"><pre class="sourcelines wrap"> <span id="l1.1" class="minusline">--- a/a Thu Jan 01 00:00:00 1970 +0000</span><a href="#l1.1"></a> <span id="l1.2" class="plusline">+++ /dev/null Thu Jan 01 00:00:00 1970 +0000</span><a href="#l1.2"></a> <span id="l1.3" class="atline">@@ -1,1 +0,0 @@</span><a href="#l1.3"></a> <span id="l1.4" class="minusline">-a</span><a href="#l1.4"></a></pre></div> </div> </div> </div> </div> </body> </html> $ cd ..