Chunk loading/generation is extremely slow

The Issue

Since 1.12.2, the game performance (in terms of chunk loading) has been getting worse. 1.14.1 and 1.14.2 are nearly unplayeble (thanks to the render failures [now pretty solved] and now the extremly slow chunk load) if youre a end-game player messing around with elytra. In this report i´ll provide some footage done in near identical scenarios where you can see how bad is the performance of this recent versions.

Steps to reproduce

1. Create a creative normal word with seed: 1356868495221471351  (This is done in this seed because betwen versions a large ocean where the test is done remains, and because i wanted to recreate a normal word exploration)

2.  Turn off mob spawning and then use /kill @e

3.  Move to the location shown in the videos and tp arround 30 blocks above

4.  Wait a few seconds to let the world load all of the surroundig chunks and then sprint in the air towards the horizon.

5.  When arround 1000 blocks where travelled, delete the map and repeat the process in any of the affected versions.

6.  Compare the performance between versions.

Footage

All this footage has been filmed in the same pc at the same time, trying to minimize possible variations in conditions of the test.

Most important and significant videos will be the "fly" ones. Chart ones are there to show the game performance.

• 1.12.2 Videos

  • https://youtu.be/mSuK2zDDPU4 "Fly"

  • https://youtu.be/K2HLmfLOnkw "Chart1"

  • https://youtu.be/Q6uhyObBaBg "Chart2"

• 1.14.1 Videos

  • https://youtu.be/y6Ur-4m8XsE "Fly"

  • https://youtu.be/ugKaghUDGeo "Chart1"

  • https://youtu.be/Tsuz5jPKSWU  "Chart2"

• 1.14.2pre2

  • https://youtu.be/wk9YNw_o97k  "Fly"

  • https://youtu.be/gkQpOJlpnl4  "Chart1"

  • https://youtu.be/SZImSXU8S2Q  "Chart2"

I hope thas this becomes playable, because we are having such a bad experience with the 1.14 so far. Thanks for the hard work. Keep it up Mojang! 😉