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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/118587/">https://git.reviewboard.kde.org/r/118587/</a>
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<p style="margin-top: 0;">On June 6th, 2014, 10:59 a.m. UTC, <b>David Faure</b> wrote:</p>
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<a href="https://git.reviewboard.kde.org/r/118587/diff/1/?file=279295#file279295line109" style="color: black; font-weight: bold; text-decoration: underline;">kdecore/config/kconfigini.cpp</a>
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(Diff revision 1)
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">KConfigIniBackend::parseConfig(const QByteArray& currentLocale, KEntryMap& entryMap,</pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="c1">// This is often the case, especially sub groups will all have</span></pre></td>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">This isn't always the case though. kmail does that, yes, but e.g. kdeglobals doesn't.
Nor most desktop files, nor konquerorrc (except that some video player added per-file groups into mine!).
What do we lose if the config file has no repeated keys? Memory (the hash) and CPU (inserting and looking up into the hash), right?
I have a hard time being sure that the tradeoff is always in our favour.</pre>
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<p>On June 6th, 2014, 11:04 a.m. UTC, <b>Milian Wolff</b> wrote:</p>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Yes, the tradeoff is the memory of the hash-internal structure (which is temporary!).
Looking at my konquerorrc, I still see tons of shared strings: false and true :) Then all the stuff in the toolbar configuration, esp. the keys used there.
Also: konquerorrc and other config or desktop files are small. It might be slowed down by this patch, but not by much. It will not become a hotspot suddenly. But the cases where this already is an issue right now, this patch helps a lot.</pre>
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<pre style="margin-left: 1em; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Looking at the cache hit/miss ratio in Konqueror:
after startup:
HIT 7629
MISSED 5863
after shutdown:
HIT 11153
MISSED 6485
so even there this is worth it.
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<p>- Milian</p>
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<p>On June 6th, 2014, 9:31 a.m. UTC, Milian Wolff wrote:</p>
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<div>Review request for kdelibs and David Faure.</div>
<div>By Milian Wolff.</div>
<p style="color: grey;"><i>Updated June 6, 2014, 9:31 a.m.</i></p>
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<b style="color: #575012; font-size: 10pt;">Repository: </b>
kdelibs
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Optimize KConfigIniBackend::parseConfig by reducing allocations.
Yet another awesome application of the Qt implicit sharing trick.
Since config files often contain only few different keys and even
value strings, we can share them. This reduces memory consumption
and also speeds up parsing, as we do not have to allocate the
duplicated strings, but can simply reuse the previous values.
The most extreme case for this of my knowledge, is KatePart:
katesyntaxhighlightingrc has more then 20k lines which triggered
about 30k allocations on startup. With this patch applied, this
value goes down dramatically. I added a simple static counter for
the cache hit/miss ratio, which resulted in 5442 cache misses compared
to 43624 cache hits across all KConfig files parsed by kwrite on startup.
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Unit tests all pass. My malloc tracer shows that the allocations are all gone.
My malloc tracer showed before:
17421 allocations at:
0x7fee73692b97 QByteArray::QByteArray(char const*, int) /usr/lib/libQtCore.so.4
0x7fee73bb7cee ? /usr/lib/libkdecore.so.5
0x7fee73bb7fc4 ? /usr/lib/libkdecore.so.5
0x7fee73ba1320 ? /usr/lib/libkdecore.so.5
0x7fee73ba1731 KConfig::KConfig(QString const&, QFlags<KConfig::OpenFlag>, char const*) /usr/lib/libkdecore.so.5
0x7fee64830c06 KateHlManager::KateHlManager() in /ssd/milian/projects/kde4/kate/part/syntax/katesyntaxmanager.cpp:76 /ssd/milian/projects/compiled/kde4/lib/libkatepartinterfaces.so.4
12699 allocations at:
0x7fee73692b97 QByteArray::QByteArray(char const*, int) /usr/lib/libQtCore.so.4
0x7fee73bb7cd7 ? /usr/lib/libkdecore.so.5
0x7fee73bb7fc4 ? /usr/lib/libkdecore.so.5
0x7fee73ba1320 ? /usr/lib/libkdecore.so.5
0x7fee73ba1731 KConfig::KConfig(QString const&, QFlags<KConfig::OpenFlag>, char const*) /usr/lib/libkdecore.so.5
0x7fee64830c06 KateHlManager::KateHlManager() in /ssd/milian/projects/kde4/kate/part/syntax/katesyntaxmanager.cpp:76 /ssd/milian/projects/compiled/kde4/lib/libkatepartinterfaces.so.4
These where the allocation hotspots number #1 and #3 respectively. With the patch applied, the two locations are not under the top 10 anymore.</pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
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<li>kdecore/config/bufferfragment_p.h <span style="color: grey">(5a753ad)</span></li>
<li>kdecore/config/kconfigini.cpp <span style="color: grey">(8ec43c5)</span></li>
<li>kdecore/config/kconfigini_p.h <span style="color: grey">(d7aa43e)</span></li>
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<p><a href="https://git.reviewboard.kde.org/r/118587/diff/" style="margin-left: 3em;">View Diff</a></p>
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