The v.2.3.1 version of Additional Structures mod linked bellow causes cascading worldgen lag, by itself it wouldn't be that bad but in any sizeable modpack it adds on quite a bit of cascading worldgen lag. I have also included a link explaing exactly what that is and how to go about fixing it. Example setting and offset or flags when structures are spawned partially in a chunk and when adjesent chunks load it reads it and finishes generating the structure.
The v.2.3.1 version of Additional Structures mod linked bellow causes cascading worldgen lag, by itself it wouldn't be that bad but in any sizeable modpack it adds on quite a bit of cascading worldgen lag. I have also included a link explaing exactly what that is and how to go about fixing it. Example setting and offset or flags when structures are spawned partially in a chunk and when adjesent chunks load it reads it and finishes generating the structure.
https://www.reddit.com/r/feedthebeast/comments/5x0twz/investigating_extreme_worldgen_lag/
https://www.curseforge.com/minecraft/mc-mods/additional-structures/files/2810589