title: CADisplayLink causes the lag between touchesBegan and touchesEnded?
body: <p>I use a CADisplayLink (running at 20 FPS) to redraw my Opengl ES scene. As I do this, I found that there is a huge lag between touchesBegan and touchesEnded on touch events, almost 200 ms or more. </p>
  
  <p>If I turn off the CADisplayLink then the lag is reduced to 50 ms. Any one know how to fix this issue?</p>