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

[Michael Pyne]

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I like the idea, and the code changes LGTM. But I think the autotest can be improved by ensuring that the short-term caching of the 'unknown' status of a non-existent icon works, instead of just ensuring that the cache is ignored once enough time has elapsed.

i.e. something like

    // find non-existent icon
    // verify its null
    // install test icon (don't reset time-to-elapse yet)
    
    // find previously-non-existent icon
    // verify it's reported as null (this means we're caching its status)
    // reset time-to-elapse to zero

    // find previously-non-existent icon again
    // verify it's valid and exists

I suppose this would make it more of a case of how it's implemented than what it's meant to do, but since caching the unknown-edness of a non-existent icon is what actually gives us the speedup we want, I think it makes sense to make sure we don't accidentally break that later.

- Michael Pyne


On July 16, 2016, 9:52 a.m., David Faure wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/128465/
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> 
> (Updated July 16, 2016, 9:52 a.m.)
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> 
> Review request for KDE Frameworks, Christoph Feck, David Rosca, Michael Pyne, and Olivier Goffart.
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> Repository: kiconthemes
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> 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
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>   autotests/kiconengine_unittest.cpp 105e86c1e7bc6170c626aa80d34cdb6422acca9c 
>   src/kiconloader.cpp d885318c166f2a996b038218366317615886a14e 
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> Diff: https://git.reviewboard.kde.org/r/128465/diff/
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> Testing
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> (described in commit log)
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> 
> Thanks,
> 
> David Faure
> 
>

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