Review Request: Implemented multithreading in KFileItemModelSortAlgorithm

[Mark Gaiser]

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dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.cpp
<http://git.reviewboard.kde.org/r/107025/#comment16470>

    Ehh for a 2 core system this would result in 0.. 
    
    And with the numberIfThreads / 2 you apparently want to prevent a situation where one sorts a massive folder and all cpu threads get used to do the sorting..
    
    Then why don't you just do this:
    if (numberOfThreads > 2) {
      const int newNumberOfThreads = numberOfThreads - 1;
      ...
    }
    
    That would allow you to always have one thread free for the other stuff. Thus this implementation will never get executed on dual core systems, only on 2+ core systems. And with that it takes as much threads as it can (again, leaving 1 thread free for other apps).


I also like to ask to postpone merging this feature for now! Not for long, just one or two weeks. I really like to implement the suggestion of Christoph Feck from the KFM-Devel mailing list (in the thread: "Ideas for improving sorting. Goal: under 1 second for 200.000 files."). That might speed up the sorting massively and make multithreading it completely pointless. Why pointless? Well, if the sorting operation can be done under a second for such huge folders then i doubt multithreading is going to speed it up much more.

Again, this is - at this moment - just an idea on the list which i'm trying to implement right now.

- Mark Gaiser


On Oct. 25, 2012, 2:14 p.m., Emmanuel Pescosta wrote:
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> http://git.reviewboard.kde.org/r/107025/
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> (Updated Oct. 25, 2012, 2:14 p.m.)
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> 
> Review request for Dolphin and Frank Reininghaus.
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> Description
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> Implemented multithreading in KFileItemModelSortAlgorithm.
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> If more than 100 items to sort and ideal thread count is greater than 1 -> sort them with parallelSort (2 Threads)
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> Use maximal 2 Threads, because more than 2 Threads are "slower" (more overhead than speed up). (I also have a patch which uses n Threads for sorting, if you want test it ;)
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> Diffs
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>   dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.h 3a596df 
>   dolphin/src/kitemviews/private/kfileitemmodelsortalgorithm.cpp e0aac13 
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> Diff: http://git.reviewboard.kde.org/r/107025/diff/
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> Testing
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> About 2 seconds faster with sorting 500.000 files.
> About 5 seconds faster with sorting 1.000.000 files.
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> 
> Thanks,
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> Emmanuel Pescosta
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>

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