linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Mike Rapoport <rppt@linux.vnet.ibm.com>
To: Jonathan Corbet <corbet@lwn.net>
Cc: Randy Dunlap <rdunlap@infradead.org>,
	linux-doc <linux-doc@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>
Subject: [PATCH v2 11/11] docs/mm: add description of boot time memory management
Date: Sat, 30 Jun 2018 17:55:06 +0300	[thread overview]
Message-ID: <1530370506-21751-12-git-send-email-rppt@linux.vnet.ibm.com> (raw)
In-Reply-To: <1530370506-21751-1-git-send-email-rppt@linux.vnet.ibm.com>

Both bootmem and memblock are have pretty good internal documentation
coverage. With addition of some overview we get a nice description of the
early memory management.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
---
 Documentation/core-api/boot-time-mm.rst | 92 +++++++++++++++++++++++++++++++++
 Documentation/core-api/index.rst        |  1 +
 2 files changed, 93 insertions(+)
 create mode 100644 Documentation/core-api/boot-time-mm.rst

diff --git a/Documentation/core-api/boot-time-mm.rst b/Documentation/core-api/boot-time-mm.rst
new file mode 100644
index 0000000..03cb164
--- /dev/null
+++ b/Documentation/core-api/boot-time-mm.rst
@@ -0,0 +1,92 @@
+===========================
+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. To address this, a specialized allocator
+called the :ref:`Boot Memory Allocator <bootmem>`, or bootmem, was
+introduced. Several years later PowerPC developers added a "Logical
+Memory Blocks" allocator, which was later adopted by other
+architectures and renamed to :ref:`memblock <memblock>`. There is also
+a compatibility layer called `nobootmem` that translates bootmem
+allocation interfaces to memblock calls.
+
+The selection of the early allocator is done using
+``CONFIG_NO_BOOTMEM`` and ``CONFIG_HAVE_MEMBLOCK`` kernel
+configuration options. These options are enabled or disabled
+statically by the architectures' Kconfig files.
+
+* Architectures that rely only on bootmem select
+  ``CONFIG_NO_BOOTMEM=n && CONFIG_HAVE_MEMBLOCK=n``.
+* The users of memblock with the nobootmem compatibility layer set
+  ``CONFIG_NO_BOOTMEM=y && CONFIG_HAVE_MEMBLOCK=y``.
+* And for those that use both memblock and bootmem the configuration
+  includes ``CONFIG_NO_BOOTMEM=n && CONFIG_HAVE_MEMBLOCK=y``.
+
+Whichever allocator is used, it is the responsibility of the
+architecture specific initialization to 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. And more recent and
+advanced memblock even allows controlling its own behaviour.
+
+.. _bootmem:
+
+Bootmem
+=======
+
+(mostly stolen from Mel Gorman's "Understanding the Linux Virtual
+Memory Manager" `book`_)
+
+.. _book: https://www.kernel.org/doc/gorman/
+
+.. kernel-doc:: mm/bootmem.c
+   :doc: bootmem overview
+
+.. _memblock:
+
+Memblock
+========
+
+.. kernel-doc:: mm/memblock.c
+   :doc: memblock overview
+
+
+Functions and structures
+========================
+
+Common API
+----------
+
+The functions that are described in this section are available
+regardless of what early memory manager is enabled.
+
+.. kernel-doc:: mm/nobootmem.c
+
+Bootmem specific API
+--------------------
+
+These interfaces available only with bootmem, i.e when ``CONFIG_NO_BOOTMEM=n``
+
+.. kernel-doc:: include/linux/bootmem.h
+.. kernel-doc:: mm/bootmem.c
+   :nodocs:
+
+Memblock specific API
+---------------------
+
+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
+   :nodocs:
diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
index f5a66b7..93d5a46 100644
--- a/Documentation/core-api/index.rst
+++ b/Documentation/core-api/index.rst
@@ -28,6 +28,7 @@ Core utilities
    printk-formats
    circular-buffers
    gfp_mask-from-fs-io
+   boot-time-mm
 
 Interfaces for kernel debugging
 ===============================
-- 
2.7.4


  parent reply	other threads:[~2018-06-30 14:57 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-30 14:54 [PATCH v2 00/11] docs/mm: add boot time memory management docs Mike Rapoport
2018-06-30 14:54 ` [PATCH v2 01/11] mm/bootmem: drop duplicated kernel-doc comments Mike Rapoport
2018-06-30 14:54 ` [PATCH v2 02/11] docs/mm: nobootmem: fixup " Mike Rapoport
2018-06-30 14:54 ` [PATCH v2 03/11] docs/mm: bootmem: fix kernel-doc warnings Mike Rapoport
2018-06-30 14:54 ` [PATCH v2 04/11] docs/mm: bootmem: add kernel-doc description of 'struct bootmem_data' Mike Rapoport
2018-06-30 14:55 ` [PATCH v2 05/11] docs/mm: bootmem: add overview documentation Mike Rapoport
2018-06-30 14:55 ` [PATCH v2 06/11] mm/memblock: add a name for memblock flags enumeration Mike Rapoport
2018-07-12  8:00   ` Michal Hocko
2018-06-30 14:55 ` [PATCH v2 07/11] docs/mm: memblock: update kernel-doc comments Mike Rapoport
2018-06-30 14:55 ` [PATCH v2 08/11] docs/mm: memblock: add kernel-doc comments for memblock_add[_node] Mike Rapoport
2018-06-30 14:55 ` [PATCH v2 09/11] docs/mm: memblock: add kernel-doc description for memblock types Mike Rapoport
2018-06-30 14:55 ` [PATCH v2 10/11] docs/mm: memblock: add overview documentation Mike Rapoport
2018-06-30 14:55 ` Mike Rapoport [this message]
2018-07-03 12:23   ` [PATCH v2 11/11] docs/mm: add description of boot time memory management Michal Hocko
2018-07-12  7:26     ` Mike Rapoport
2018-07-01 15:26 ` [PATCH v2 00/11] docs/mm: add boot time memory management docs Randy Dunlap
2018-07-02 17:32 ` Jonathan Corbet
2018-07-18 11:47   ` Mike Rapoport
2018-07-18 12:02     ` Jonathan Corbet
2018-07-18 17:00       ` Mike Rapoport
2018-07-26 21:45         ` Jonathan Corbet
2018-08-02 18:36           ` Jonathan Corbet

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1530370506-21751-12-git-send-email-rppt@linux.vnet.ibm.com \
    --to=rppt@linux.vnet.ibm.com \
    --cc=corbet@lwn.net \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=rdunlap@infradead.org \
    --subject='Re: [PATCH v2 11/11] docs/mm: add description of boot time memory management' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).