Performance: Essential Must-Knows
From The DarkMod Wiki
written by Fidcal
Caulk
Textured brush surfaces that are hidden by patches or behind beams etc. still add to the rendering complexity. So to improve performance those surfaces should be textured with common > caulk because that texture is not rendered at all.
There is no need to use caulk texture on on any surfaces on the outside of the map in contact with the void because these will automatically be unrendered.
Render-Sectioning using Visportals
If visportals are not used then the entire map will be rendered at once wherever the player is - greatly reducing performance to the point where most maps are not likely to be playable at all. It is crucial that the map should be compartmentalized using visportals. Study the Visportals tutorial for details.