Huge Pages in PostgreSQL
Your server keeps a page table — a structure in RAM whose only job is to describe where other memory lives. Every process has its own, with one 8-byte entry per 4 KB page it has actually touched. In PostgreSQL every connection gets its own backend, and every backend is a separate OS process — so each one keeps a private description of the same shared_buffers. The more memory you give the database and the more connections you run, the more RAM disappears into simply describing memory you already own. On a production box that is routinely 10–20 GB.