Overview#
Minecraft does a lot of its heavy work - world generation, chunk loading, saving and other background jobs - on a pool of worker threads that run across your CPU cores. By default the game decides how many of those threads to create and what priority they run at.
Thread Tweak lets you take control of that pool. You can change how many background worker threads Minecraft uses and what thread priority they run at, which can help the game share the CPU more nicely with the rest of your system. It only affects thread scheduling - it does not change any gameplay.
What You Can Change#
Thread Tweak exposes two kinds of settings:
| Setting | What it does |
|---|---|
| Thread count (main) | How many background worker threads Minecraft's main pool uses |
| Thread priority (main) | The OS priority of those background worker threads |
| Thread priority (io) | The priority of the input/output (file) worker threads |
Lowering the worker priority makes Minecraft yield CPU time to other programs more readily, while changing the thread count controls how much of the CPU the background pool can use at once.
Configuration File#
Thread Tweak is configured through a JSON file. The first time you run the game with the mod installed, it creates:
.minecraft/config/threadtweak.jsonThe file looks like this:
{
"threadCount": { "bootstrap": 1, "main": 7 },
"threadPriority": { "game": 5, "bootstrap": 1, "main": 1, "io": 1, "integratedServer": 5 }
}Edit the numbers, save the file, and restart Minecraft for the changes to take effect. Thread priorities are clamped to the range 1-10, and the main thread count defaults to one less than your number of CPU cores.
Tuning Tips#
- On a many-core CPU, the defaults are usually fine; the mod mainly helps if you want the game to be a background task while doing other things.
- To make Minecraft less greedy with the CPU, keep the worker priority low (the default is already 1) so other apps stay responsive.
- If you see stutters while lots of chunks are generating, experimenting with the main thread count can help balance throughput against smoothness.
- Changes only apply on game start, because the worker pools are built once, very early in loading.
Notes#
- Thread Tweak works on both the client and dedicated servers.
- It is a pure performance/scheduling tweak - it adds no blocks, items or gameplay changes and is safe to add to or remove from existing worlds.
- Results vary by hardware: the mod gives you the controls, but the best values depend on your CPU and what else you run alongside the game.
- It is the modern continuation of the older Smooth Boot mod, rebuilt for the latest Minecraft versions.
