Overview docker has a significant lag to update. About 2 seconds on a picture 1600 x 1200 pixels. I'm not having other performance issues in Krita. This happens while changing layer visibility or on brush strokes. While painting sometimes I have to toggle visibility several times to check if the changes look good so it bothers a little. I tried to send the performance log but couldn`t find it.
This is actually by design, since continuously updating the overview image comes at a performance cost. But we probably reset the timer every time a stroke is made, which means that if you're busy drawing, the overview docker never gets updated.
The correct solution here would be to use KisView or KisCanvas as a second view on the image. This updates at the opengl level, so without any delay.
changing this to a wishlist item