I'm running Minecraft with Mariculture 1.2.2b and a few other mods with worldgen (Underground Biomes, Biomes O' Plenty, ExtraBiomesXL, Better Dungeons, Ruins, etc) and noticed worldgen taking an usually long time. When generating a world for the first time this could be as long as 4 or 5 minutes in some cases! I launched jvisualvm, attached it to Minecraft, and turned CPU sampling on to observe what was taking up so much time. According to jvisualvm, mariculture.world.BlockCoral.isValidFloor() was using 30-50% of the CPU during worldgen.

Nothing I can do about it, in 1.6 without rewriting the way generation is done, but at this point in 1.6 lifecycle that isn't something I'm going to do. I believe it's much better in 1.7, where I have changed how it's done. Just turn off the world module if it bothers you so much.

I know for a fact that I don't cause that long generation though, my generation for the coral may take up a lot of cpu, when it's doing the generation, but it doesn't actually take very long. My worlds don't take very long to create. (Underground Biomes is the one that will cause the long load time).