This should be one of the highest priority bugs in 1.8, as it causes a lot of lag for many maps and superflat worlds. A lot of players will complain about the new found lag in certain situations, so this bug should be fixed ASAP. Please help us, Mojang
This is a duplicate of this bug:
https://bugs.mojang.com/browse/MC-58120
Setting the gamerule doMobSpawning to false removes a lot of the performance issues. Also, here is a video of the issue:
https://www.youtube.com/watch?v=kOxq3RhIOyw
The issue is strongest in open air worlds or a superflat world with the setting 3;minecraft:barrier;1;
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.
The video I recorded is up. Here is the link: https://www.youtube.com/watch?v=kOxq3RhIOyw
8. I will try lowering it, if that is what you are suggesting.
Edit: I lowered it to 2, and nothing changed.
Thank you for your time.