QDirIterator has become significantly slower in Qt 6.8.2, relative to Qt 6.5.3. The new version is on the order of 4-5 times slower than the previous version.  I understand that QDirIterator is now wrapping the new QDirListing class, and it appears that the QDirListing class is doing a lot more work than the previous QDirIterator native Impl.

Additional information is available via my post at the Qt forum...
https://forum.qt.io/topic/161349/qdiriterator-much-slower-on-qt-6-8

My wild guess would be that perhaps QDirListing should not be calling GetFileAttributesExW for each item in the iterator, instead only calling FindNextFileW? However I have no real insight I'm just guessing about an optimal design and comparing a superliminal capture form 6.5.3 and comparing it to 6.8.2

Repro steps:

Execute the a QDirIterator similar to..

QHash<QString, MyFileUtil::FileStat> result;
    for(QDirIterator it(sourcePath, QDir::Files, QDirIterator::Subdirectories); it.hasNext(); )
    {
        it.next();
        result.insert(it.filePath(), MyFileUtil::FileStat(it.fileInfo()));
    } 

Where

MyFileUtil::FileStat(const QFileInfo& fileInfo)
    : mSize(fileInfo.size())
    , mLastModified(fileInfo.lastModified().toMSecsSinceEpoch())
{} 

on 6.5.3 and 6.8.2.

The 6.8.2 version will end up being around 5 times slower than the 6.5.3 version, even removing the construction of the FileStat object is possible to reduce the total amount of work being done.