Smooth Boot is no longer needed since version 1.19.4!

Because Minecraft has fixed this problem itself.

Link to Forge version

Smooth Boot - Optimize Minecraft loading performance to be smoother on low end systems and scale better on high end systems.

Available on Fabric and Forge for Minecraft 1.14-1.19.3.

If you have a PC with a older or lower end CPU (ex. CPUs with 8 or less threads), you may have noticed that Minecraft takes up 100% of the CPU when loading into the title screen, causing cursor stutter and makes multitasking painfully difficult. Smooth Boot solves this problem completely, and loading should be much smoother and potentially faster as well.

Features

Change amount of threads used for loading
Change priority of threads used by Minecraft
Auto config menu to change config from in game

How the mod works

Minecraft uses executors to run multithreaded tasks. The problem is that the tasks that are ran during loading are quite heavy on the CPU, so it leads to 100% CPU usage. And, some of the tasks do not necessarily benefit from multithreading. Smooth Boot fixes these problems by change the parameters of the executors, including the number of threads they use and the priority of each thread.

For more information, please read the Smooth Boot wiki

Compatibility

The mod should be compatible with all mods including Optifine. However, it's worth noting that the mod uses mixin overwrites on some methods used for loading the game. If you run into incompatibility issues, please leave a comment.

Smooth Boot (Fabric)