[MC-239474] Autosaving now causes extreme and gameplay-impacting lag

In 21w42a, whenever the world autosaves, there's a huge lag spike compared to auto-saving in 21w41a. This issue also causes legitimate gameplay issues, as mobs are able to attack the player some time before the world unfreezes, resulting in unfair deaths. I've noticed that it gets even laggier if you've mined some blocks and moved away from spawn as well.

Steps to reproduce:
1. Open a world.
2. Punch some trees and move away from spawn.
3. Wait for the autosave.
Expected behavior: The game will autosave as usual, with little to no lag.
What actually happens: The game freezes for a few second, and mobs can attack the player before the game unfreezes.

Linked issues

is duplicated by 9

MC-240770 Game lags, locks up and then crashes when Autosaving. Resolved

MC-241192 1.18 Pre Release-1. "Saving Game" causes heavy slowdown and crashes Resolved

MC-241295 Poor performance (and game crash) during autosave on 1.18 pre-1 [Minecraft Java] Resolved

MC-241570 Immensize Lag Spikes while saving world Resolved

MC-241608 Snapshot world crashing shortly after starting game Resolved

4 more links

Attachments

Comments 16

anthony cicinelli 2021-10-21T13:32:41Z

We do not have enough information to find the cause of this issue.

While the lag occurs, please run /debug start, wait a while and then run /debug stop in order to create a debug profile. Afterwards, run /debug report.

If you do not have the permission to run these commands, open your world to LAN and enable cheats. If you're on a server, make sure that you're a server operator in order to execute these commands.

Then, please attach the profile results found in [minecraft/debug/profile-results-<DATE>.txt|https://minecrafthopper.net/help/finding-minecraft-data-folder/], as well as the debug report found in [minecraft/debug/debug-report-<DATE>.zip|https://minecrafthopper.net/help/finding-minecraft-data-folder/] here.

_{This issue is being temporarily closed as}_{Awaiting Response}_{. Once the requested information has been delivered, the report will be reopened automatically.}

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Lunade Lunade 2021-10-21T14:22:19Z

I loaded a world with cheats. /debug start/stop are there, but there's no /debug report. On top of that, I can't run any commands during an autosave, because the game freezes. Either way, there are still freezes from autosaving, which sometimes still result in unfair deaths and confusing gameplay.

[media]

CalXee 2021-10-23T15:32:24Z

Can confirm, that 9000ms server lag spike was during the autosave.

Sachari 2021-10-23T15:40:11Z

Can confirm

Ceresjanin123 2021-10-23T17:24:35Z

Can confirm, all entities freeze for me until the autosave is done

6 more comments

Arma Geddon 2021-10-27T14:29:32Z

I don't think I have experienced an auto-save, actually. I thought that was only on Bedrock editions.

billysjoberg 2021-10-28T08:37:49Z

Thanks all.
This is a known issue when saving ticking blocks and liquids that should be at least somewhat mitigated by a fix in 21w43a snapshot.
Would you mind trying the latest snapshot and comparing the save time duration?

Lunade Lunade 2021-10-28T13:26:34Z

I'd say it's roughly down to 1/3 of the time of 21w42a's saving, definitely a great improvement!
Sadly, it still causes some lag and freezing between 1-3 seconds. It does still impact gameplay- although a lot less compared to 21w42a.

Edit: I don't know if it's possible, but I think autosaving should be able to freeze mob AI. I just loaded a world and the autosave happened- a spider warped to me and hit me right when the autosave finished. Although it wasn't a big deal, I'm sure there are some situations in the game where that would spell the end for some players.

Justin Coulston 2021-11-12T15:41:29Z

Can confirm the same issue on 1.18 pre-1 my end in most cases the game then crashes

MisteryGates 2021-11-15T18:10:11Z

Can confirm. I hope mojang will fix all lag problems that happens in 1.18.

Richard Greenawalt 2021-11-15T23:29:28Z

I had not noticed the lag spike on the 21W42a snapshot, but Pre 1 freezes and crashes when auto saving. Screen locks up and JVM utilization jumps to 98-100% and then the processes suspends. Terrain, mob and plant updates are saved, but user inventory data is not.

I am playing a new vanilla game.

Sugel Perez Contreras 2021-11-16T16:54:46Z

I have discovered something that may help. I was having this issue consistently then I modified the installation for 1.18 pre-1 in the launcher to change memory allocation from 2GB (default) to 16GB. I now no longer experience crashes or severe lag spikes (actually performance has improved dramatically). My machine has 64GB of RAM so I could easily spare it. While running the game it shows sometimes up to 55% memory usage (of the 16GB now allocated). This is effected also by view distance which I have set to 32 chunks currently.

Sugel Perez Contreras 2021-11-16T17:50:10Z

That may be, but this release, 1.18 pre1, was totally unplayable for me until I increased the memory allocation from the default 2GB to 16GB. Before that it would choke badly at every autosave and nearly always crash while the autosave was in progress. I do not see how these issues are not related. Also this was a problem for save and exit as well. No form of saving the game did not lead to crash and burn. After increasing memory allocation I don't even experience lag on autosave.

SeaOfPixels 2021-11-16T20:45:10Z

It might be that this has always been happening, but it's just become super apparent now that the autosave has an indicator. Still something I think should be optimized though.

Richard Anglin 2021-11-18T19:02:24Z

Fixed in new snapshots but still kinda laggy.

Pieter Maes 2024-02-25T02:24:26Z

on Minecraft 1.20.4

When more than 10K chunks are loaded, the autosave (every 5 min) maxes out nvme's for a couple of seconds and hangs ticks with the can't keep up warning (including vehicles rubber banding during the save)