MC-185363sync-chunk-writes often takes over a minute to close a world
Apologies if this has been reported before, I searched for "save" and "saving" and could not find anything relevant.
This issue has occurred since 20w14a. There is a workaround on a server, to disable sync-chunk-writes, but there is no workaround in singleplayer.
To reproduce in singleplayer, start a world and close it again, observe that the world can take tens of seconds to close. To reproduce on a dedicated server, start the server and type stop in the console, and observe that the server hangs for a bit after printing the "saving chunks for level" message.
Given that this hasn't been reported yet, I'm assuming it may be operating system dependent, although I haven't tested this on other operating systems. My OS is Ubuntu 18.04 (see the environment section).
I ran the server through VisualVM. I have attached a screenshot of part of the profile results, as well as a CSV containing the entire snapshot.
Environment
Ubuntu 18.04
openjdk version "1.8.0_252"
OpenJDK Runtime Environment (build 1.8.0_252-8u252-b09-1~18.04-b09)
OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)
Linked Issues
Created Issue:
Worlds take a very long time to close
Apologies if this has been reported before, I searched for "save" and "saving" and could not find anything relevant.
This issue has occurred for a new snapshots now, but wasn't an issue in the last release, 1.15.2.
To reproduce in singleplayer, start a world and close it again, observe that the world can take tens of seconds to close. To reproduce on a dedicated server, start the server and type stop in the console, and observe that the server hangs for a bit after printing the "saving chunks for level" message.
Given that this hasn't been reported yet, I'm assuming it may be operating system dependent, although I haven't tested this on other operating systems. My OS is Ubuntu 18.04 (see the environment section).
I ran the server through VisualVM, and at first glance it seems like a race condition where two threads are trying to close the same output stream. I have attached a screenshot of part of the profile results, as well as a CSV containing the entire snapshot.
Environment
Ubuntu 18.04
OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)
Attachments2
Ubuntu 18.04
openjdk version "1.8.0_252"
OpenJDK Runtime Environment (build 1.8.0_252-8u252-b09-1~18.04-b09)
OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)
![[Mod] Michael Wobst](../../../data/avatars/users/37868.png){kind=small}
Apologies if this has been reported before, I searched for "save" and "saving" and could not find anything relevant.
This issue has occurred for a
new snapshots now, but wasn't an issue in the last release, 1.15.2.To reproduce in singleplayer, start a world and close it again, observe that the world can take tens of seconds to close. To reproduce on a dedicated server, start the server and type stop in the console, and observe that the server hangs for a bit after printing the "saving chunks for level" message.
Given that this hasn't been reported yet, I'm assuming it may be operating system dependent, although I haven't tested this on other operating systems. My OS is Ubuntu 18.04 (see the environment section).
I ran the server through VisualVM, and at first glance it seems like a race condition where two threads are trying to close the same output stream. I have attached a screenshot of part of the profile results, as well as a CSV containing the entire snapshot.
Apologies if this has been reported before, I searched for "save" and "saving" and could not find anything relevant.
This issue has occurred for a few snapshots now, but wasn't an issue in the last release, 1.15.2.
To reproduce in singleplayer, start a world and close it again, observe that the world can take tens of seconds to close. To reproduce on a dedicated server, start the server and type stop in the console, and observe that the server hangs for a bit after printing the "saving chunks for level" message.
Given that this hasn't been reported yet, I'm assuming it may be operating system dependent, although I haven't tested this on other operating systems. My OS is Ubuntu 18.04 (see the environment section).
I ran the server through VisualVM, and at first glance it seems like a race condition where two threads are trying to close the same output stream. I have attached a screenshot of part of the profile results, as well as a CSV containing the entire snapshot.
Apologies if this has been reported before, I searched for "save" and "saving" and could not find anything relevant.
This issue has occurred
for a few snapshots now, but wasn't an issue in the last release, 1.15.2.To reproduce in singleplayer, start a world and close it again, observe that the world can take tens of seconds to close. To reproduce on a dedicated server, start the server and type stop in the console, and observe that the server hangs for a bit after printing the "saving chunks for level" message.
Given that this hasn't been reported yet, I'm assuming it may be operating system dependent, although I haven't tested this on other operating systems. My OS is Ubuntu 18.04 (see the environment section).
I ran the server through VisualVM
, and at first glance it seems like a race condition where two threads are trying to close the same output stream. I have attached a screenshot of part of the profile results, as well as a CSV containing the entire snapshot.Apologies if this has been reported before, I searched for "save" and "saving" and could not find anything relevant.
This issue has occurred since 20w14a. There is a workaround on a server, to disable sync-chunk-writes, but there is no workaround in singleplayer.
To reproduce in singleplayer, start a world and close it again, observe that the world can take tens of seconds to close. To reproduce on a dedicated server, start the server and type stop in the console, and observe that the server hangs for a bit after printing the "saving chunks for level" message.
Given that this hasn't been reported yet, I'm assuming it may be operating system dependent, although I haven't tested this on other operating systems. My OS is Ubuntu 18.04 (see the environment section).
I ran the server through VisualVM. I have attached a screenshot of part of the profile results, as well as a CSV containing the entire snapshot.
Worlds take a very long time to closesync-chunk-writes often takes over a minute to close a world
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Thanks, we're already tracking this in MC-185363.
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Thank you for your report, please add your specs to MC-185363! Thank you! 
This is most likely caused by the recent changes to the world saving logic.
After testing various server versions, I can now say that this bug was introduced in 20w14a.
Aha, it's fixed by turning setting `sync-chunk-writes` to `false` in `server.properties`.
I will update the bug report to mention that `sync-chunk-writes` seriously needs optimizing, and also point out that there is no way to disable it in singleplayer (and no progress bar).
This is still an issue in 1.16pre1
Adding info from my ticket per request: