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  1. Minecraft: Java Edition
  2. MC-1692

Excessive lag on lamp de/activation across chunk borders


    • Icon: Bug Bug
    • Resolution: Fixed
    • Minecraft 18w43a
    • Minecraft 1.4.2, Minecraft 1.4.6, Minecraft 1.4.7, Snapshot 13w06a, Snapshot 13w10b, Minecraft 1.5, Minecraft 1.5.2, Minecraft 1.6.2, Minecraft 1.6.4, Minecraft 13w38b, Minecraft 13w38c, Minecraft 13w39a, Minecraft 1.7.2, Minecraft 1.7.4, Minecraft 14w05b, Minecraft 14w06b, Minecraft 14w07a, Minecraft 1.7.10, Minecraft 14w32a, Minecraft 14w32b, Minecraft 14w32c, Minecraft 14w32d, Minecraft 14w33a, Minecraft 1.8, Minecraft 1.8.1-pre2, Minecraft 1.8.1-pre4, Minecraft 1.9 Pre-Release 1, Minecraft 1.9.1, Minecraft 1.9.2, Minecraft 1.10.2, Minecraft 1.11, Minecraft 1.11.2, Minecraft 17w06a, Minecraft 1.12.1, Minecraft 1.12.2, Minecraft 17w50a
    • Confirmed

      See this video by Teekeks for a demonstration of this issue.


      Redstone lamps turning on and off cause an unusually large amount of FPS lag when on/near chunk borders. While there is still some (expected) lag in the middle of a chunk, the amount on chunk borders is significantly higher.


      1. Enable chunk border rendering with F3+G
      2. Enable the lagometer and debug profiler by pressing Alt+Shift+F3.
      3. In the middle of a chunk, build an 6x6 pad of redstone lamps, and place redstone dust on those lamps.
      4. Connect those lamps to a fast clock (such as 2 repeaters pointing into each other)
      5. Observe that there is a slight lag spike each time the lamps turn on.
      6. Disconnect that system, and then build a similar 6x6 pad at the intersection of 4 chunk borders (such that there is a 3x3 area in each chunk)
      7. Connect that system to a fast clock
      8. Observe the much higher FPS drop


      • The profiler node "scheduledExcecutables.checkLight.checkedPosition < toCheckCount" is the most time-consuming one when this issue is in effect.

            fry [Mojang] Georgii Gavrichev
            martok Martok
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