[kernel] page table data

https://en.wikipedia.org/wiki/Page_table

Page table data:

• frame table
  holds information about which frames are mapped. In more advanced systems, the frame table can also hold information about which address space a page belongs to, statistics information, or other background information.
• page table
  holds the mapping between a virtual address of a page and the address of a physical frame. There is also auxiliary information about the page such as a present bit, a dirty or modified bit, address space or process ID information, amongst others.
• The present bit can indicate what pages are currently present in physical memory or are on disk, and can indicate how to treat these different pages, i.e. whether to load a page from disk and page another page in physical memory out.

https://en.wikipedia.org/wiki/Single_address_space_operating_system

• Single address space operating system
  A single address space operating system (or SASOS) is an operating system that provides for all processes only one globally shared virtual address space.