Hi. Whenever I optimize a large world Minecraft will freeze for me while doing the necessary backup.
Steps to Reproduce:
Click on Optimize World (1.12 world)
Click 'Backup and Load'
See how Minecraft will freeze after a while.
OR:
Click on Edit World
Click 'Make Backup'
See how Minecraft will freeze after a while.
For the test purpose I used the Białowieża Forest map showcased on Minecraft.net some time ago. This world is about 18GB large (~8GB bigger than our average server worlds). It will however finish doing the backup after a while and then start to run the chunk upgrade process which runs smoothly again.
I've also uploaded a picture showcasing the problem. Yeah, my CPU is at 99%, but Minecraft had two full threads and about 10% of my CPU for this task so this shouldn't be a problem (while the OS drive and the drive Minecraft is installed on had also little work to do). The problem here seems to be (just guessing) that the backup process is being done in the same thread as the render thread instead of a worker thread.
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Ok, I just added the launcher log to the issue (after it appeared again. After the backup was done and thus the world upgrade happens I clicked cancel as the world upgrade itself isn't affected).
Afterwards I tested it again with the same world and it happened again (look at screenshot-1 for details). For this test I also decided to have the log output window open to better see what the log put's out when it occurs and afterwards.
Also note that whether this issue occurs depends on the world size. Smaller worlds aren't affected, thought I haven't figured out the smallest necessary world size for the issue too occur, thus I'm always going with the largest map I've got as I know that it will definitly happen on this map size.
I've also found out, the issue also applies to the normal backup functionality of Minecraft (see the updated description of the issue) and worlds as small as 460MB on my SSD also cause the issue to occur, so no need for a multiply gigabyte world to force this issue to occur (at least on my system).
This happens for me as well. It is because the game is not running the backup on a second thread, so it is freezing while it is copying the files.
I've removed the environment field of this ticket since this problem here doesn't appear to be environmentally exclusive. 🙂
Can confirm in 1.19.4-pre4. As Alan said, the game becomes completely unresponsive and if you are fullscreened you can't tab out to other programs, which is quite frustrating.
Something i noticed is the game unfreezes and finishes the backup in windowed mode, however it forces me to force close the program on fullscreen.
We do not have enough information to find the cause of this issue.
After having this issue, please attach the full launcher log file found in
[.minecraft/launcher_log.txt|http://hopper.minecraft.net/help/guides/minecraft-logs/]here.