Boats cause massive lag in the end game

June 4, 2021

Known Issue

We host 5 DST servers and one of them is endless server. The endless server has had massive lag spike if run it in long term. Today, I spotted weird thing in htop.

Normal CPU usage is usually around 10% for one shard of DST in idle state in day 0-30. However, our endless server uses 50-52% of CPU while being idle. TheSim is paused. This is 5x worse performance in idle.

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I have been ~~investigating~~ debugging the thing that can cause the lag by simple removing the items with the largest count:

items  = {}
for i, k in pairs(Ents)  do 
 if k.prefab then
   if items[k.prefab] == nil then 
    items[k.prefab] = 0
   end
    items[k.prefab] = items[k.prefab] + 1
  end
end
max = 0 
max_i = ''
for i,k in pairs(items) do 
 if k > max  then 
    max = k
    max_i = i
 end 
end
c_announce(max_i)
c_announce(max)
c_removeall(max_i)

However firstly, I just removed all the inventory items (prefabs that have inventoryitem component), there were 5500 inventory items. I bet some of them were floating in the water, e.g. seeds, or white logs. The CPU went on 42% but it was NOT enough.

After removing 351x bullkelp_plant_leaves, and bullkelp_plant, the CPU went on 32-34%.

There is 209x [boat_player_collision, boat_item_collision, walkingplank, boatlip, boat]. The CPU went below 10%.

Steps to Reproduce

See issue description. Save file: http://dontfight.club/test/boatlag.zip