[mirror_ubuntu-hirsute-kernel.git] / Documentation / core-api / boot-time-mm.rst

===========================
Boot time memory management
===========================

Early system initialization cannot use "normal" memory management
simply because it is not set up yet. But there is still need to
allocate memory for various data structures, for instance for the
physical page allocator.

A specialized allocator called ``memblock`` performs the
boot time memory management. The architecture specific initialization
must set it up in :c:func:`setup_arch` and tear it down in
:c:func:`mem_init` functions.

Once the early memory management is available it offers a variety of
functions and macros for memory allocations. The allocation request
may be directed to the first (and probably the only) node or to a
particular node in a NUMA system. There are API variants that panic
when an allocation fails and those that don't.

Memblock also offers a variety of APIs that control its own behaviour.

Memblock Overview
=================

.. kernel-doc:: mm/memblock.c
   :doc: memblock overview


Functions and structures
========================

Here is the description of memblock data structures, functions and
macros. Some of them are actually internal, but since they are
documented it would be silly to omit them. Besides, reading the
descriptions for the internal functions can help to understand what
really happens under the hood.

.. kernel-doc:: include/linux/memblock.h
.. kernel-doc:: mm/memblock.c
   :functions:
Commit	Line	Data
ae9d8845 MR	1	===========================
	2	Boot time memory management
	3	===========================
	4
	5	Early system initialization cannot use "normal" memory management
	6	simply because it is not set up yet. But there is still need to
	7	allocate memory for various data structures, for instance for the
530d4c0c	8	physical page allocator.
ae9d8845	9
530d4c0c MR	10	A specialized allocator called ``memblock`` performs the
	11	boot time memory management. The architecture specific initialization
	12	must set it up in :c:func:`setup_arch` and tear it down in
	13	:c:func:`mem_init` functions.
ae9d8845 MR	14
	15	Once the early memory management is available it offers a variety of
	16	functions and macros for memory allocations. The allocation request
	17	may be directed to the first (and probably the only) node or to a
	18	particular node in a NUMA system. There are API variants that panic
530d4c0c	19	when an allocation fails and those that don't.
ae9d8845	20
530d4c0c	21	Memblock also offers a variety of APIs that control its own behaviour.
ae9d8845	22
530d4c0c MR	23	Memblock Overview
530d4c0c MR	24	=================
ae9d8845 MR	25
	26	.. kernel-doc:: mm/memblock.c
	27	:doc: memblock overview
	28
	29
	30	Functions and structures
	31	========================
	32
ae9d8845 MR	33	Here is the description of memblock data structures, functions and
	34	macros. Some of them are actually internal, but since they are
	35	documented it would be silly to omit them. Besides, reading the
	36	descriptions for the internal functions can help to understand what
	37	really happens under the hood.
	38
	39	.. kernel-doc:: include/linux/memblock.h
	40	.. kernel-doc:: mm/memblock.c
ad98b602	41	:functions: