Faye N

Yes, I don't install mods for snapshots.

I encountered this as well. I tried teleporting to a place where Allays are meant to be, and the chunks wouldn't load. I was stuck in Creative mode (what I was in before teleporting) and couldn't switch to Survival or Spectator mode through the F3+F4 shortcut. Then I tried hitting save & quit, and I ended up stuck on the "Saving world..." screen, and had to kill the game.

Teleporting a second time while in Survival mode had me falling forever, showing that the game thinks the place is completely devoid of blocks. I also found that trying to teleport away or use the /locatebiome command gave absolutely no response, however you can move around, at least if you teleported in creative mode and use its ability to fly around. (You'll need to use the F3 screen's coords to verify you're moving, of course.)

There wasn't any CPU activity by the game after I teleported over, so it feels like the game was waiting for some condition to be met (as opposed to getting stuck processing something forever).

Since this was marked as "can't reproduce", I'll share some details in case this issue is more specific to my world than I initially assumed. The world seed is 235379857779490613, and the snowy terrain in question can be found at 1329 / / -127. I had mapped out all but a few map pixels' worth of this snowy area in 1.16 (though I'd guess there's not much difference between that and how it would've generated in 1.17, and I can't say for certain there aren't some 1.17 chunks here and there). I had last left my save at 609 / / -642, and so all my tests of this world in the prereleases start from there. (There is, of course, already-explored terrain connecting that start point to the tundra.)

I've also got another JFR recording showing a trip in pre4. Relevant timestamps are 1637313244 for when I started walking on snow and 1637313675 for when I stood still (until the end of the recording). Again, the standing still is to help show that the memory usage remains high, and it's not just the result of constantly asking the game to work on yet more chunks.

The memory usage still climbs over time when exploring the terrain, but I couldn't get the game to enter a freezing loop in pre4. Pauses occurred a couple times, but they were all one-time things. Loading the level back up and walking over terrain I had walked over before showed no issues, as I'd noticed before, so it definitely seems like a one-time issue around updating chunks.

Point is, it's definitely a lot better than it was before. I'm not worried about how to work around the issue when 1.18 comes out in full anymore, but there's still something being left behind in memory. I can capture a new JFR for pre4 later if that would be useful.

Problem still exists in 1.18 prerelease 2, though it did seem to take longer to get the game to enter that freezing loop. I also noticed that pressing F3+A (just to see if reloading chunks would clear out memory) didn't help the issue, but it did drop the amount of used RAM needed to lock up the screen, curiously. When testing this time, the game would lock up for a second whenever the F3 screen reported about 1900 MiB used, but after hitting F3+A it would instead lock up when it said about 1800 MiB. Not sure if that means anything, but I figured I'd mention it just in case.

I don't think so, since that bug is about using some kind of structure in a new world, while this bug only crops up in old worlds and doesn't require adding any additional content to the world beyond what the vanilla game comes with. Additionally, that bug describes something that takes 24 hours (real time or in-game?) to trigger, while this under the right conditions takes just 10 real world minutes. They could possibly be the same issue underneath, but I feel like only a dev would be able to find that out.

Still an issue in 1.17.1. I'd like to add that single-sapling trees of any kind will grow just fine in snow-covered places, it's just 2x2 spruce and jungle trees that can't. 2x2 dark oak does work, however.

I've noticed this as well on Linux with a Radeon RX 5600. Unlike the original report I cannot make the borders show up at all.

Edit: while playing some more with this debug setting left on, I suddenly started seeing the black-only border lines from certain, quite finicky angles. I should note that it's possible to make them appear in first-person view as well as third-person.