OpenGL picture update in 5.3.0 very slow

I've just upgraded from 5.2.1 to 5.3.0 and the OpenGL updates have become very slow. For example, in the example hellogl if I move the mouse very rapidly to rotate the image, the rotation lags and takes a second or two to catch up when I stop moving the mouse. The same example compiled with 5.2.1 is instantly responsive. I've hacked a version of the openglwindow example to similarly rotate with the mouse and that shows the same behaviour, so I would guess it is not specific to the old QGLWidget.