Review Request 128465: KIconLoader: massive speed improvement for loading unavailable icons

[David Faure]

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https://git.reviewboard.kde.org/r/128465/
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(Updated July 17, 2016, 8:14 p.m.)


Review request for KDE Frameworks, Christoph Feck, David Rosca, Michael Pyne, and Olivier Goffart.


Changes
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Merge into a single hash, and avoid double lookups.


Repository: kiconthemes


Description
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Summary:
The code said "unknown icons should be searched for anew each time
[so that installing new icons works]". However this leads to massive
performance issues when opening the file dialog in a dir with many
files for which there is no mimetype icon.
In my case, 293 callgrind.out.* files in one dir (it's ironic that
they would create a huge performance issue...).

To make both sides happy (installing new icons should still work, but
still unknown icons shouldn't lead to a full disk search every time
icon.isNull() or icon.pixmap() is called), let's re-resolve unknown
icons again only after 5 seconds.

Benchmark results for loading an unavailable icon :
before: 43 msecs per iteration    (1897 disk locations checked)
after: 0.013 msecs per iteration  (pixmap found in the on-disk cache)
And the file dialog no longer crawls to a halt in the dir with 293 callgrind files.

Test Plan:

Reviewers:

Subscribers:


Diffs (updated)
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  autotests/kiconengine_unittest.cpp 105e86c1e7bc6170c626aa80d34cdb6422acca9c 
  src/kiconloader.cpp d885318c166f2a996b038218366317615886a14e 

Diff: https://git.reviewboard.kde.org/r/128465/diff/


Testing
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(described in commit log)


Thanks,

David Faure

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