Virtual Memory and Memory Management | Knowledge Base by Andrii Sonsiadlo

📄️The address space

A pointer on x86-64 is a 64-bit value, but the address space it names is not a 64-bit space. Implementing

Translation is a size problem before it's anything else. A flat table mapping every 4 KiB page of a

Page Tables and the Walk established that a translation costs up to

The Virtual Address Space described the layout a process's pointers

The Life of a Page Fault told this story shallowly, as

The Page Fault Handler named doanonymouspage() and dowppage() as

Every other allocator in the kernel — slab, vmalloc, the page cache, the stack allocator — ultimately

The Page Allocator deals in 4 KiB units. The kernel allocates `struct

Every allocation decision in the kernel eventually comes down to one distinction: physically

struct page describes one 4 KiB frame of physical memory, and there is one struct page for every

This is the single most consequential piece of Linux memory management, and the one most misread by

There is a gap between "the write returned" and "the data is safe", and most data-loss incidents live

The Page Allocator hands out pages until it can't. A system that only

Swap has an undeserved reputation. It is not "what happens when a machine runs out of memory" — it is

By the time this code runs, every allocation path has already failed, reclaim has already been asked and

A TLB holds a fixed number of entries, and its reach — the amount of address space it can translate

Node-local allocation by default, the policies that override it, and when NUMA effects are a red herring.

How to actually answer "how much memory is this using", and why every simple answer to that question is wrong.