Mercurial > hg
view tests/test-hgweb-removed.t @ 38732:be4984261611
merge: mark file gets as not thread safe (issue5933)
In default installs, this has the effect of disabling the thread-based
worker on Windows when manifesting files in the working directory. My
measurements have shown that with revlog-based repositories, Mercurial
spends a lot of CPU time in revlog code resolving file data. This ends
up incurring a lot of context switching across threads and slows down
`hg update` operations when going from an empty working directory to
the tip of the repo.
On mozilla-unified (246,351 files) on an i7-6700K (4+4 CPUs):
before: 487s wall
after: 360s wall (equivalent to worker.enabled=false)
cpus=2: 379s wall
Even with only 2 threads, the thread pool is still slower.
The introduction of the thread-based worker (02b36e860e0b) states that
it resulted in a "~50%" speedup for `hg sparse --enable-profile` and
`hg sparse --disable-profile`. This disagrees with my measurement
above. I theorize a few reasons for this:
1) Removal of files from the working directory is I/O - not CPU - bound
and should benefit from a thread pool (unless I/O is insanely fast
and the GIL release is near instantaneous). So tests like `hg sparse
--enable-profile` may exercise deletion throughput and aren't good
benchmarks for worker tasks that are CPU heavy.
2) The patch was authored by someone at Facebook. The results were
likely measured against a repository using remotefilelog. And I
believe that revision retrieval during working directory updates with
remotefilelog will often use a remote store, thus being I/O and not
CPU bound. This probably resulted in an overstated performance gain.
Since there appears to be a need to enable the thread-based worker with
some stores, I've made the flagging of file gets as thread safe
configurable. I've made it experimental because I don't want to formalize
a boolean flag for this option and because this attribute is best
captured against the store implementation. But we don't have a proper
store API for this yet. I'd rather cross this bridge later.
It is possible there are revlog-based repositories that do benefit from
a thread-based worker. I didn't do very comprehensive testing. If there
are, we may want to devise a more proper algorithm for whether to use
the thread-based worker, including possibly config options to limit the
number of threads to use. But until I see evidence that justifies
complexity, simplicity wins.
Differential Revision: https://phab.mercurial-scm.org/D3963
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 18 Jul 2018 09:49:34 -0700 |
parents | 82ae4f471254 |
children |
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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="phase">draft</span> <span class="branchhead">default</span> <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" class="diffstattoggle" href="#">[<tt>+</tt>]</a> <div id="diffstatdetails" style="display:none;"> <a class="diffstattoggle" href="#">[<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="#">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="phase">draft</span> <span class="branchhead">default</span> <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="#">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 ..