Question about queued chunk updates

What are they? Are they supposed to (ideally) stay around 0? I’ve noticed my FPS drops considerably as the number of queued chunk updates stacks up. Sometimes they take several minutes to drop back down to 0 once they stack up to like 500 or so. Is this normal behavior? So, overall, would a good metric for if DH is able to keep up with the movement of the player be if the queued chunk updates stay close to 0 during movement?