Understanding the “game clock”

Understanding how your server ticks underneath can be helpful when diagnosing problems regarding slow performance. We’ll cover several topics.

  1. An overview of the game logic loop
  2. How this all applies to modded servers
  3. An explanation of transient problems
  4. A guide to profiling your server
  5. A macro-view of improving performance

The game logic loop

The most important part of Minecraft is the game loop. In there is a clock keeping everything synchronized, going tick-tock at an ideally constant rate: twenty times per second, with each tick or tock lasting hopefully at most 50 milliseconds. During each cycle, game elements have to do their work — skeletons have to figure out where to walk, minecarts have to travel forward, grass has to spread, and light problems have to be checked. That’s a lengthy to-do list, considering how many blocks and entities are on a loaded world at at time (thousands). This tick-tock interval is called the tick rate or “TPS,” and you can get some mod or plugin to give you your server’s rate.

vanilla

Quite a few things are on the to-do list, but as far as the “main game elements” go, those items are blocks, entities, and tile entities. Blocks include simple things such as sandstone, cobble, sugar cane, and things of that nature. Entities are your standard animals and monsters, in addition to paintings, item drops, and “objects that don’t fit perfectly on a grid.” Tile entities are a special kind of block, as they can hold any type of data (think storing an inventory, something sugar cane doesn’t have to do), and sometimes they must think separately. As previously mentioned, each loop has a budget of 50ms and each portion consumes some part of this pie. Any leftover time is considered idle.

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