Add a note about huge pages to our Postgres doc (#11467)

* Add note to postgres doc about hugepages

* Newsfragment

changelog.d/11467.misc

@@ -0,0 +1 @@
+Add a note about postgres memory management and hugepages to postgres doc.

docs/postgres.md

@@ -118,6 +118,9 @@ performance:
 Note that the appropriate values for those fields depend on the amount
 of free memory the database host has available.
 
+Additionally, admins of large deployments might want to consider using huge pages
+to help manage memory, especially when using large values of `shared_buffers`. You
+can read more about that [here](https://www.postgresql.org/docs/10/kernel-resources.html#LINUX-HUGE-PAGES).
 
 ## Porting from SQLite