[MC-63630] Major Performance Issues in Open Air Superflat Worlds

Expected:
Entities move at normal speeds and minecraft performs fine in a superflat world with just a level of barrier blocks.

Found:
Everything in that barrier superflat world moves at a slower pace, making it frustrating to play. Entities even fall at very slow rates.

Replication:
1. Create a superflat world with the gen set as 3;minecraft:barrier;1;
2. Spawn slimes and observe as they slowly jump around.

Linked issues

What is your render distance set to?

ShadowofElements 2014-07-25T02:19:36Z

8. I will try lowering it, if that is what you are suggesting.

Edit: I lowered it to 2, and nothing changed.

You can try, but I wanted to see if you had it set really high because that causes lag. (by high, I mean 20-30)

ShadowofElements 2014-07-25T02:45:02Z

The video I recorded is up. Here is the link: https://www.youtube.com/watch?v=kOxq3RhIOyw

ShadowofElements 2014-07-25T12:41:01Z

It seems that setting the gamerule doMobSpawning to false removes a lot of the performance issues. This could help in finding the cause of this bug.