Using addons, giving a mob like the Slime the ability to destroy blocks with a large "breakable _blocks" list can cause immense slowdowns when there are more than 6 of them at once in render distance. Tick speed is reduced massively and the game can eventually become unplayable and crash in multiplayer if there are too many mobs with this behavior.
The blocks they destroy has a 100% chance of dropping its item counterpart, however this does minimal to affect the tick speed. It seems the list itself is treated inefficiently, which is the cause of the slowdowns.
"minecraft:break_blocks":{
"breakable_blocks":[
"minecraft:grass","minecraft:grass_path","minecraft:dirt",
"minecraft:podzol","minecraft:mycelium",
"minecraft:red_mushroom_block","minecraft:brown_mushroom_block",
"minecraft:planks","minecraft:log","minecraft:leaves",
"minecraft:cobblestone","minecraft:mossy_cobblestone",
"minecraft:gravel","minecraft:smooth_stone", "minecraft:hay_block","minecraft:wheat","minecraft:potatoes",
"minecraft:carrots","minecraft:beetroot","minecraft:melon",
"minecraft:pumpkin","minecraft:sweet_berry_bush","minecraft:cake",
"minecraft:tallgrass","minecraft:brown_mushroom","minecraft:red_mushroom",
"minecraft:acacia_stairs","minecraft:birch_stairs",
"minecraft:dark_oak_stairs","minecraft:jungle_stairs",
"minecraft:oak_stairs","minecraft:spruce_stairs",
"minecraft:cobblestone_stairs","minecraft:mossy_cobblestone_stairs", "minecraft:stripped_acacia_log","minecraft:stripped_birch_log",
"minecraft:stripped_dark_oak_log","minecraft:stripped_jungle_log",
"minecraft:stripped_oak_log","minecraft:stripped_spruce_log",
"minecraft:wooden_slab","minecraft:stone_slab",
"minecraft:fence","minecraft:wooden_door",
"minecraft:glass","minecraft:glass_pane",
"minecraft:stained_glass","minecraft:stained_glass_pane"
]
}
Comments 2
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I've tested this in multiplayer. The tick speed reduces to an unbearable crawl with the only way to recover is through killing all mobs with this behavior. The tick speed reaches to a minimum of 1 tick per second. Completely unplayable in a large server, but does not immediately crash fortunately.