I can confirm it was definitely happening on my Cave Spider farm on 20w20b, and it's still happening in 1.16-Pre2 as well.
As the amount of exp. orbs present decreased from the 300s to the 200s and 100s, the framerate finally went back to normal.
This issue is no longer happening on my end as of 1.14 Pre-Release 4. I haven't really checked the Pre-Release 3, but I guess that's irrelevant now.
Just like before, I'm still getting block lag in 1.14 Pre2. I don't know if this is relevant, but if I break a block and I move onto breaking another block right away, when the first block finally falls to the ground it resets the progress I had breaking the 2nd one.
I'm getting block lag in the 1st pre-release of the 1.14 version on Single Player, and it might be related to this issue.
On my end, it takes 5 seconds for me to get an Oak Log after breaking it with a Wooden Axe.
I break the block, it regenerates and stays there for a second or two, and then the item is dropped for me to pick it up.
Can confirm, it still happens in 1.14 Pre1.
Confirmed for 19w14b. I had to stop walking and wait for a minute before the next chunk got generated in a world that I quickly created within that snapshot.
EDIT: Also, these are my Game Settings, in case they're needed.
It looks like this was fixed, at least on my end. In the Snapshot 19w14b, hostile mobs are finally spawning around my base during Night Time with Render Distance set to 5 Chunks.
Confirmed for 19w13b. Hostile mobs are still not spawning during night time with Render Distance set to 5 chunks.
Can confirm. At first I thought that I just got another performance hit due to my weak hardware (the 1.14 snapshots have some pretty long loading times compared to 1.12.2 or even 1.13.2), but looking at this open issue, I guess I wasn't the only one affected.
Can confirm, chunk generation works awfully bad on the latest snapshot.
I don't know if it's directly related to this bug or not, but it is also overall laggy on my end. Playing on Single Player feels like playing on a bad quality Multiplayer Server. Loading times in general are quite atrocious, a block takes a few seconds to drop to the floor, getting into the Nether takes a while, and when you reach the Nether it has serious issues loading up, I couldn't even fight a single Zombie Pigman because it got stuck in the air after hitting him once with a Stone Axe.
In comparison, every single thing works perfectly fine with the same configuration and the same JVM arguments on the version 1.12.2 of the game (no mods, not even Optifine).
Blocks fall to the floor instantly after breaking them and going to the Nether doesn't even take a full minute.
Specs: Intel Celeron N2840, Intel HD Graphics, Windows 8.1 (x64).
Config: https://i.imgur.com/kMWIhmI.png
Notes: In the Launcher I have the path to Java SE Runtime Environment 8u201 for 32 Bits set in Java Settings - Executable in both of my profiles (one for the Snapshots and one for Stable Releases).
I also use the following JVM Arguments, again, in both profiles: -Xmx1G -XX:+UseConcMarkSweepGC -XX:-UseAdaptiveSizePolicy -Xmn128M -XX:+UnlockExperimentalVMOptions -XX:ParallelGCThreads=2
Confirmed for 19w09a here too. I have the Render Distance set to 5 and I just couldn't find a single hostile mob in the areas surrounding my house. Playing on Normal difficulty.
I came here to comment that the workaround provided in this issue helped me to fix a weird glitch where the percent sign in the Music & Sound Settings turned into a white square. Thanks!