VideoklipBG

Can confirm, I was able to reproduce this multiple times. Strangely the first time there was no crash report generated. The second time occurred around X: 1500 / Z: 9500 on seed 7710288261028957899. Archive with the world, log and crash reports, and also the first log without crash report.

Confirmed for 20w09a

Confirmed for 20w09a

Confirmed for 20w09a

Can confirm for 20w09a

Can confirm for 20w09a

Can confirm for 20w09a

@Kamil Pigłowski @MetoolDaddy Yes, I can confirm that disabling mob AI and/or spawning greatly improved the performance in certain scenarios like mob farms, large spaces with spawn-able platforms, etc. However, the server performance overall seems to have dipped way down in recent versions (1.13 / 1.14), compared to older stable versions like 1.11 and 1.12.

According to my observations and tests the major hit in performance, as expected, is still caused by chunk generation/loading, entities, mob spawning and AI.

This ticket is focused primarily on that, along with some additional info on how the gameplay is affected. I don't really know if the stated details cover too large area, but if other tickets contain all specific points that are listed here, maybe this one should be split and carried over?

To be honest, there are way too many small bits of details about performance issues in hundreds of tickets to keep track of, let alone filter and create separate report for every single one.

I'm open to suggestions on what could be changed here, or if the mods decide to close and split the ticket if needed.

I was just testing similar issue (MC-138550) and I'm still able to reproduce this in different situations with different settings, more noticeable with render distance of 16 and above. I can definitely say, though, that this issue was way worse in some of the previous snapshots.

@unknown's video demonstrates exactly what I'm experiencing, maybe the ticket's description isn't as clear.

In my opinion, the problem might be that most people with mid and lower-end hardware could experience some consequences of this issue, like freezes or even crashes. I personally don't, and yes, this ticket doesn't state anything related to actual crashes. But even the game running on high-end hardware (like in my case), there are still big performance problems, one of which is this.

Chunk loading in 1.13.2 was certainly faster, it had bigger hit on the server performance (TPS) and a bit on the client (FPS), although flying quickly in creative mode or with an elytra wasn't a problem at all. Currently these actions lead to loading chunks unable catch up, the server struggling to keep running smoothly, and it's even worse when generating new, undiscovered chunks.

According to my observations, it seems like the chunk generation / loading was most likely moved to the end of each tick (or the idle time) to avoid delaying more important tasks. This might or might not be the cause of this issue in particular, but at least there should be some balance between performance and responsiveness. 1.13.2 and older versions were decent in terms of these two things, however the previous snapshots and these pre-releases, according to most people and me, definitely need more tweaking and optimization.

I appreciate the developers' hard work and effort to polish the upcoming release and fix as many bugs as possible, and would be glad to provide assistance or any additional information if necessary.

These two debug logs are from different locations in a new world generated on 1.14 pre-2, exploring around a bit in creative mode, visiting structures (mostly villages, pyramids, ocean ruins, etc.) and staying in different places for a while. Noticed very bad periodic TPS drops and consistently high execution time, along with the server completely hanging for 10-20 seconds once in a while, most likely due to autosave. This was exceptionally worse throughout the second logging period.

Can confirm, generating a new world on singleplayer or multiplayer results in random chunks spontaneously turning dark from top to bottom. Optimizing the world and clearing the cached data temporarily fixes the issue, but not for long.

Edit: Added screenshots with F3 open + newly generated world on 1.14 Pre-2 with glitched lighting

1.14 Pre-2 world with glitched lighting

Confirmed for 1.14 Pre-Release 1 and Pre-Release 2.

@unknown Double checked and tested everything thoroughly, I can reproduce it consistently in the latest snapshot (currently 19w14b). Updated the information and the video demonstrating the issue.

After short duration of playtime I've noticed that the tick execution time rises continuously until the game starts to compensate by massively slowing down chunk loading, world interaction, physics, and eventually skipping ticks. This appears to be the exact same case for a lot of the previous snapshots, including 19w13.

5 minutes of exploring:

15-20 minutes of exploring:

Abnormal execution time (happens rarely, complete world reload / server restart is required to fix it):

The gradual increase makes me think this may have something to do with the tick idle time?
Also MC-138114, MC-132135 and MC-139717 might be related.

Seems like 19w11a made this much worse.

Affects all 18w40 snapshots and 18w50a

Seems to be fixed in 18w48a

Can confirm for 18w47a

Confirmed for 18w46a and 18w47a 

Oh, my bad, I looked briefly at the reports and because one was crash-client, while the other one crash-server I created separate tickets. Also apparently forgot to attach the client crash report here.