Bug 157266

Thanks for the detailed description, I was not aware about this performance issue. I've added David Faure to CC, as I cannot explain why the number of sub directories influences the loading time of the directory "a" containing only 20 directories. Maybe the part to blame is that for each directory the "Sizes" column is filled with the number of sub items inside this directory. My guess would be that this information should already be part of the directory node, but maybe some more expensive things are done. I'll check this when I find some time doing some Dolphin work this week, but maybe David has already a hint.

@David: I did some tests and the performance issue only occurs if the "Size" column is shown (e. g. in the details view). I had a look at KDirModel::data() and I guess the bottleneck is in the ChildCountRole case:

case ChildCountRole:
if (!item.isDir())
    return ChildCountUnknown;
else {
    KDirModelDirNode* dirNode = static_cast<KDirModelDirNode *>(node);
    int count = dirNode->childCount();
    if (count == ChildCountUnknown && item.isReadable()) {
        const QString path = item.localPath();
        if (!path.isEmpty()) {
            QDir dir(path);
            count = dir.entryList(QDir::AllEntries|QDir::NoDotAndDotDot|QDir::System).count();
            //kDebug(7008) << "child count for " << path << ":" << count;
            dirNode->setChildCount(count);
        }
    }
    return count;
}

QDir::entryList() returns a string-list of all (!) directory entries and we just need the directory count... Isn't there a faster way getting the number of directories (e.g. ls -l for sure does not take care about this)? My guess is that QDir::count() should be fixed, but maybe there is a straight forward way to bypass this performance issue at least on Unix systems by directly asking the filesystem instead of using QDir?

Does this work faster?
(I tested that it works, but I'll let you check if it helps in terms of performance)


Created an attachment (id=23462)
kdirmodel.cpp.diff

Thanks David for the patch. I don't have time until the weekend for testing it but I'll respond as soon as I've some numbers...

David, I've tested you're patch and it makes it a lot faster. Previously it took around 2 seconds until my test folders appeared, now the folder is shown immediately (at least I can see no performance difference in comparison with a folder having no sub directories).

SVN commit 774075 by dfaure:

Much faster implementation of ChildCountRole. Peter tested it and said:
"Previously it took around 2 seconds until my test folders appeared, now the folder is shown immediately (at least I can see no performance difference in comparison with a folder having no sub directories)."
BUG: 157266


 M  +19 -0     kdirmodel.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=774075