Uploaded image for project: 'Minecraft: Java Edition'
  1. Minecraft: Java Edition
  2. MC-151082

Loading chunks creates irrecoverable lag (restart required)


    • Icon: Bug Bug
    • Resolution: Awaiting Response
    • Minecraft 1.14, Minecraft 1.14.1 Pre-Release 1, Minecraft 1.14.2, Minecraft 1.14.3 Pre-Release 3, Minecraft 1.14.4 Pre-Release 6, 1.14.4, 19w42a, 1.16.3, 1.16.4 Release Candidate 1, 1.16.4, 20w46a, 1.17, 1.17.1 Pre-release 1
    • None
    • Community Consensus
    • Chunk loading
    • Important
    • Platform

      Moderator Note

      For those still experiencing this problem, please run the following commands while the lag is occurring:

      /debug start
        wait some time while the lag is occurring
      /debug stop

      /debug report

      Once complete, navigate to the debug directory inside the game directory, and attach the resulting profiler and debug report files to this report.

      The chunk-loading was addressed in MC-149178 and marked as "fixed" but I beg to differ. The mod comments in that report recommended creating a new report for 1.14.1, so here we go.

      Lag is caused by loading chunks, and remains until the server is restarted. This generally takes several thousand blocks of travelling to replicate with a single player online, but can quickly bring a multiplayer server to its knees after just a few hours of standard gameplay.

      In all of the following test cases, I am connecting to a remote vanilla server with a vanilla client. The server is hosted on hardware that is entirely separate from the client that is connecting to it.


      Case #1

      Buffet cave world with mob spawning enabled and 512MB of memory

      Video: https://youtu.be/Zosu1BPpl6w

      10:15 - See the lag in action (see case_1_during_lag.debug.txt)
      12:15 - And how it disappears after rebooting the server (see case_1_after_reboot.debug.txt)


      Case #2

      Default world with mob spawning disabled and 1GB of memory

      Video: https://youtu.be/AaGVQvC1vW4

      20:50 - After travelling 16k blocks, the lag does not seem to have appeared (see case_2_before_lag.debug.txt)
      23:30 - After travelling 20k blocks, the lag has appeared (see case_2_during_lag.debug.txt and case_2_during_lag.log.txt)
      30:50 - The lag persists despite several different methods of attempting to alleviate it
      36:00 - After rebooting the server, the lag no longer exists (see case_2_after_reboot.debug.txt and case_2_after_reboot.log.txt)

            Unassigned Unassigned
            Arcensoth Arcensoth
            122 Vote for this issue
            67 Start watching this issue