Collisions cause extreme lag

Since 1.9, massive entities in one spot (+400 for me, depends on your computer/server) cause extreme lag. To fix this, just make a 3x3 spot (or more) where will be your entities instead of a 1x1. Or kill them.

How to reproduce:
https://www.youtube.com/watch?v=Vty2f53Ocfc&feature=youtu.be