Reduce unnecessary world-generation load and test city settings methodically. This guide focuses on a repeatable setup process rather than assuming every launcher, modpack or server uses the same files.
Keep the generator stable
Frequent changes to profiles or large collections of world-generation mods can make performance testing noisy. Benchmark one stable configuration at a time.
Generate in controlled sessions
Rapid exploration can force many chunks to generate at once. Give the server or client time to finish generation before judging steady-state performance.
Tune the wider modpack
Performance depends on more than Lost Cities. Entity-heavy mods, shaders, high view distance and storage speed can all become bottlenecks while new terrain is generated.
Use logs and timings
Measure before changing settings. Watch memory use, tick time and repeated errors so you can target the actual bottleneck rather than guessing.