Review Request 118586: Optimize KConfigGroup::exists and similar operations.

[Oswald Buddenhagen]

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Ship it!


fwiw, this could be optimized much more reasonably if the entry map was an actual tree.
thomas braxton sent me a preliminary version of that years ago, but never finished it. are you interested in picking this up?


- Oswald Buddenhagen


On June 6, 2014, 11:22 a.m., Milian Wolff wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/118586/
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> 
> (Updated June 6, 2014, 11:22 a.m.)
> 
> 
> Review request for kdelibs, David Faure, Matthew Dawson, and Oswald Buddenhagen.
> 
> 
> Repository: kdelibs
> 
> 
> Description
> -------
> 
> Optimize KConfigGroup::exists and similar operations.
> 
> Before, these kind of read-only operations did a lot of allocations:
> 
> 1) allocate a list of all sub groups
> 2) for the above, also allocate a sub-group match key
> 3) iterate over sub groups, allocate a list of all keys in there
> and then finally check whether that list is non-empty
> 
> All of the above is now done without a single allocation, by simply
> iterating over the list of entries.
> 
> Note: The whole list was iterated even before in allSubGroups. Now
> we still do that, but check for non-empty keys in the group or
> sub group directly. Much more efficient.
> 
> Note2: While at it, allSubGroups is also optimized to not require the
> allocation of the subgroup match key.
> 
> 
> Diffs
> -----
> 
>   kdecore/config/kconfig.cpp b941983 
> 
> Diff: https://git.reviewboard.kde.org/r/118586/diff/
> 
> 
> Testing
> -------
> 
> The unit tests all run just fine. I broke it while implementing this patch, so I'm confident this functionality is actually properly tested and covered :)
> 
> The saved allocations are plenty. This is e.g. from the startup of kwrite:
> 
> 2844 allocations at:
> 0x7ff7fbc490e9 QHashData::allocateNode(int) /usr/lib/libQtCore.so.4
> 0x7ff7fc152f8e QHash<QString, QHashDummyValue>::createNode(unsigned int, QString const&, QHashDummyValue const&, QHashNode<QString, QHashDumm
> yValue>**) in /usr/include/qt4/QtCore/qhash.h:543 /ssd/milian/projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc152472 QHash<QString, QHashDummyValue>::insert(QString const&, QHashDummyValue const&) in /usr/include/qt4/QtCore/qhash.h:763 /ssd/mi
> lian/projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc1515f9 QSet<QString>::insert(QString const&) in /usr/include/qt4/QtCore/qset.h:181 /ssd/milian/projects/compiled/kde4/lib/libkdecore.
> so.5
> 0x7ff7fc1501ab QSet<QString>::operator<<(QString const&) in /usr/include/qt4/QtCore/qset.h:201 /ssd/milian/projects/compiled/kde4/lib/libkdec
> ore.so.5
> 0x7ff7fc14b4a7 KConfigPrivate::keyListImpl(QByteArray const&) const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfig.cpp:367 /ssd/
> milian/projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc14b25d KConfigPrivate::hasNonDeletedEntries(QByteArray const&) const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfig.cpp:
> 347 /ssd/milian/projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc14dfeb KConfig::hasGroupImpl(QByteArray const&) const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfig.cpp:856 /ssd/milian
> /projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc1536b4 KConfigBase::hasGroup(QByteArray const&) const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfigbase.cpp:42 /ssd/mil
> ian/projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc158fcd KConfigGroup::exists() const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfiggroup.cpp:592 /ssd/milian/projects/com
> piled/kde4/lib/libkdecore.so.5
> 
> 2844 allocations at:
> 0x7ff7fbc71426 QString::QString(int, Qt::Initialization) /usr/lib/libQtCore.so.4
> 0x7ff7fbd66820 ? /usr/lib/libQtCore.so.4
> 0x7ff7fbc737db QString::fromUtf8(char const*, int) /usr/lib/libQtCore.so.4
> 0x7ff7fc14b494 KConfigPrivate::keyListImpl(QByteArray const&) const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfig.cpp:367 /ssd/milian/projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc14b25d KConfigPrivate::hasNonDeletedEntries(QByteArray const&) const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfig.cpp:347 /ssd/milian/projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc14dfeb KConfig::hasGroupImpl(QByteArray const&) const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfig.cpp:856 /ssd/milian/projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc1536b4 KConfigBase::hasGroup(QByteArray const&) const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfigbase.cpp:42 /ssd/milian/projects/compiled/kde4/lib/libkdecore.so.5
> 0x7ff7fc158fcd KConfigGroup::exists() const in /ssd/milian/projects/kde4/kdelibs/kdecore/config/kconfiggroup.cpp:592 /ssd/milian/projects/compiled/kde4/lib/libkdecore.so.5
> 
> All of these are gone with the patch.
> 
> 
> Thanks,
> 
> Milian Wolff
> 
>

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