The Killd Board / Slimes
How many slimes does it take to crash a Minecraft server?
6,826, which makes the slime the cheapest mob anywhere on this board. Only arrows and block hoppers took more, and neither of those is a mob. It died at 30,746.
Paper 1.21.11 · AMD Ryzen 7 9700X · 6GB allocated
Why slimes cost so much
A slime does not path. It picks a direction, hops, and reconsiders when it lands. That is close to the simplest movement any hostile mob has, and skipping real navigation skips the single most expensive thing most mobs do every tick. What a slime does cost is size: a large slime has a large hitbox, so a dense pile pays a collision tax the way the iron golems did. Even with that, it took more than twice as many slimes as wardens.
How we tested it
Everything spawned into a single chunk, in one pile, with the server left running until the tick rate gave up. The server ran Paper 1.21.11 on an AMD Ryzen 7 9700X with 6GB allocated, which is the same hardware and the same RAM policy as an ordinary Hostd plan. We watched TPS and tick times rather than guessing, wrote down the count where the server first fell behind, and kept spawning until it either died or made it clear it was not going to.
A slime farm is one of the safer big farms to build. It is not free, and the chunk it sits in still matters, but per mob it is about as cheap as spawning gets.
What this means for your server
If your own server is printing Can't keep up! Is the server overloaded? the cause is the same shape as this one: something in the tick loop is taking longer than its 50ms budget. Roastd reads your RAM allocation, view distance, player slots, JVM flags and logs and names which of those it is. No account, no world upload, no charge.
Questions about slimes
Do slime farms lag a Minecraft server?
Less than most mob farms of the same size. Slimes hop rather than path, which skips the expensive part of ordinary mob AI, and our test server did not fall behind until 6,826 in a single chunk. What will still hurt is the item and experience backlog a farm produces if nothing is collecting it.
What is the cheapest mob to have thousands of?
Of everything we have tested, the slime, at 6,826 before the tick rate slipped. For comparison, wardens managed it at 1,912 and ender dragons at 605. Simple movement beats complex AI by a factor of three or more.
Elsewhere on the board
Keep reading
Rent the machine we keep breaking
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