Definition
Plain language
The computer's internal lookup table that maps a program's memory addresses to where the data actually sits in physical memory.
As stated in the literature
A kernel data structure mapping a process's virtual addresses to physical pages; fork must duplicate it even when the underlying pages are shared copy-on-write, so fork cost grows with page-table size rather than total memory.
Also called: page tables
Why it matters: It must be copied whenever a process forks, so its size, not the total memory used, can quietly drive up the cost of creating new processes.
For example, when a program asks for the data at one of its addresses, the page table is the lookup that says where in physical memory that data really lives.
Heard on the show
“The only memory cost is the kernel bookkeeping — the page tables and so on.”Episode 068 — The OS Trick That Makes Tree Search Practical for Coding Agents