1) Create fresh 1.13.2 server using world type = FLAT (chosen to simplify test case, issue also present on DEFAULT).

2) Start server, let world generate, shut it down.

3) Start server and note world loading takes ~464 ms, with full server load taking ~1.869s.

4) Repeat steps 1-2 using 18w04b.

5) Start server and note world loading takes ~3800ms, with full server load taking ~5.734s.

Bug / Expected Result:

Chunk loading performance should not be > 8x slower than previous version.

Note also: 1.12.2 does not show world load time, only total server load time. Following the same steps as above, this is 0.394s.

This means that from 1.12.2 to the current snapshot, the time taken to start the server has increased by a factor of approximately 14x.