Spigot patch: 0020 Detect, remove and warn about null tile entities.

https://github.com/EcoCityCraft/Spigot/blob/master/CraftBukkit-Patches/0020-Detect-remove-and-warn-about-null-tile-entities.patch
Spigot patch: 0021 Entity Activation Range

This feature gives 3 new configurable ranges that if an entity of the matching type is outside of this radius of any player, will tick at 5% of its normal rate.

This will drastically cut down on tick timings for entities that are not in range of a user to actually be "used".
This change can have dramatic impact on gameplay if configured too low. Balance according to your servers desired gameplay.
Disable entity activation range by default

Spigot's entity activation range feature was merged into MCPC+ in:
MinecraftPortCentral/MCPC-Plus@057ee699fed01dd5a41c5d570931d9276605e9d1

This features defines a "range that says at what distance must an entity be
near a player for it to be active."

However, in the world of mods with automation and chunkloaders this
behavior may be unexpected, so this commit disables it by default.

On the other hand, it can "massively improve performance for large servers",
so if you want to turn it on see entity-activation-range* in bukkit.yml.
MCPC+'s default is 0/0/0, vanilla Spigot's is 32/32/16 (animals/monster/misc).

More details on this feature can be found at: http://www.spigotmc.org/threads/entity-activation-range.405/