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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/118452/">https://git.reviewboard.kde.org/r/118452/</a>
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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;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">BTW: more food-for-thought is to use a <code style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: inherit;">QVarLengthArray<*, 8></code> inside UDSEntryPrivate, assuming that 8 is the common size we expect to see. That way, we get rid of the QVector allocations for up to 8 elements, at the cost of some overhead for UDSEntryPrivate where less fields are stored. That significantly improves the following two tests:</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">RESULT : UDSEntryBenchmark::createSmallEntries():
158,125,498 instructions per iteration (total: 158,125,498, iterations: 1)
RESULT : UDSEntryBenchmark::loadSmallEntries():
745,222,039 instructions per iteration (total: 745,222,039, iterations: 1)</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">but of course we need some special code where now we do <code style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: inherit;">.toList()</code>. Since before it returned <code style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: inherit;">.keys()</code>, and now you return <code style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: inherit;">.toList()</code>, I assume that is not often called anyways, so that would be OK.</p></pre>
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<p>- Milian Wolff</p>
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<p>On December 9th, 2014, 10:44 p.m. UTC, Frank Reininghaus wrote:</p>
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<div>Review request for KDE Frameworks and David Faure.</div>
<div>By Frank Reininghaus.</div>
<p style="color: grey;"><i>Updated Dec. 9, 2014, 10:44 p.m.</i></p>
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<b style="color: #575012; font-size: 10pt;">Repository: </b>
kio
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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;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">I am continuing to split up https://git.reviewboard.kde.org/r/113355/ , which attempts to make UDSEntry more efficient memory and CPU-wise, into independent parts. This is the third step after
https://git.reviewboard.kde.org/r/113591/ and https://git.reviewboard.kde.org/r/115739/ .</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">The present patch modifies the internal data storage of UDSEntry. UDSEntry contains a mapping from unsigned int keys to "Field" values, where Field is a struct that contains a QString and a long long (some keys correspond to numeric values, like size, date, etc, whereas others, like user and group, correspond to a QString).</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Currently, UDSEntry stores all data in a QHash<uint, Field> internally. This ensures that everything can be accessed in O(1) time, but is not very efficient memory-wise because a separate memory allocation is done for each hash node.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">I propose to change this and store both the uint keys and the Field values in a QVector each. This means that accessing a value becomes a O(n) operation, since the entire QVector of keys may need to be scanned in order to find a value, but because the number n of values in a UDSEntry is usually quite small and can currently not exceed a number ~100, this should not matter in practice.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Some parts of https://git.reviewboard.kde.org/r/113355/ are still missing:</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">(a) The QVectors which store the keys (which are usually the same for all items in a directory) are not shared yet. Changing this would reduce the memory usage further, but I decided to keep this change separate in order to keep the current patch small and easy to understand. Moreover, this makes it easier to benchmark other similar approaches (e.g., replace QVector by std::vector, or store keys and values together in a std::vector<std::pair<uint,Field>>).</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">(b) No space is reserved in the vectors when key/value pairs are inserted one by one. Implementing this would make UDSEntry faster on the slave side (since repeated re-allocations would not be necessary any more), but this can be done in a later patch. Moreover, it might not be needed any more if UDSEntry is not used directly any more on the slave side, as suggested on the frameworks mailing list by Aaron (good idea BTW!). </p></pre>
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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;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Unit tests still pass.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">The memory usage of listjobtest with a directory with 100,000 files is reduced from 71344 K to 35392 K according to KSysGuard. I see similar savings when opening the directory in Dolphin.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">I still haven't set up a Qt5/KF5 build in release mode (shame on me!), so I cannot present any benchmark results.</p></pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
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<li>autotests/udsentry_benchmark.cpp <span style="color: grey">(b5fa8d6)</span></li>
<li>src/core/udsentry.h <span style="color: grey">(98a7035)</span></li>
<li>src/core/udsentry.cpp <span style="color: grey">(b806e0e)</span></li>
<li>src/ioslaves/file/file.cpp <span style="color: grey">(1a2a767)</span></li>
<li>tests/udsentrybenchmark.cpp <span style="color: grey">(d9a118c)</span></li>
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<p><a href="https://git.reviewboard.kde.org/r/118452/diff/" style="margin-left: 3em;">View Diff</a></p>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">File Attachments </h1>
<li><a href="https://git.reviewboard.kde.org/media/uploaded/files/2014/12/09/038e443c-78eb-443b-b33a-b451b28d10ea__UDSEntry-benchmarks.png">Benchmark results</a></li>
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