QTableView slow scrolling

[Khaine]

I have a problem with QTableView. Model which I want to display has about 400k of samples (and it's really not much, it's supposed to work with many millions of samples). It's 27 columns with over 13k rows right now. Unfortunately scrolling is very slow. If someone moves mouse cursor quite dynamically he will have to wait good amount of time until scroll bar actually meets vertical position of cursor again. Where can I search for performance drops? What can I do to make it silky smooth? Or maybe it's qt classes that are slow? Data loads from file in an instant. It just appears immediately. Yet slowdown at scrolling is definitelly visible. If window is smaller, then scrolling is faster. It seems that's directly connected to number of samples currently being displayed on screen (rather not total number of samples inside model).