QWebview render too slow in real time application

We want to use qt to create a simple browser in a D3D based texture. The current solution is use QWebview to load webpages and interactive with mouse/keyboard input, and then use QWebview::render() that convert the current webpage to QImage, finally fill the QImage to a D3D texture.

But the fps drop from 60 to 30~40 when loading a single webpage. After checking the execution time of each block, we find that QWebView::render() cost > 0.01s on one webpage. But If I use Awesomium to render webpage, the fps will not drop.

Is there anyway to speed up QWebView::render(), or is there any other alternative solution?