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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 10/11] docs/mm: memblock: add overview documentation
Date: Sat, 30 Jun 2018 17:55:05 +0300	[thread overview]
Message-ID: <1530370506-21751-11-git-send-email-rppt@linux.vnet.ibm.com> (raw)
In-Reply-To: <1530370506-21751-1-git-send-email-rppt@linux.vnet.ibm.com>

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
---
 mm/memblock.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/mm/memblock.c b/mm/memblock.c
index 3e6be01..084f5f5 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -27,6 +27,61 @@
 
 #include "internal.h"
 
+/**
+ * DOC: memblock overview
+ *
+ * Memblock is a method of managing memory regions during the early
+ * boot period when the usual kernel memory allocators are not up and
+ * running.
+ *
+ * Memblock views the system memory as collections of contiguous
+ * regions. There are several types of these collections:
+ *
+ * * ``memory`` - describes the physical memory available to the
+ *   kernel; this may differ from the actual physical memory installed
+ *   in the system, for instance when the memory is restricted with
+ *   ``mem=`` command line parameter
+ * * ``reserved`` - describes the regions that were allocated
+ * * ``physmap`` - describes the actual physical memory regardless of
+ *   the possible restrictions; the ``physmap`` type is only available
+ *   on some architectures.
+ *
+ * Each region is represented by :c:type:`struct memblock_region` that
+ * defines the region extents, its attributes and NUMA node id on NUMA
+ * systems. Every memory type is described by the :c:type:`struct
+ * memblock_type` which contains an array of memory regions along with
+ * the allocator metadata. The memory types are nicely wrapped with
+ * :c:type:`struct memblock`. This structure is statically initialzed
+ * at build time. The region arrays for the "memory" and "reserved"
+ * types are initially sized to %INIT_MEMBLOCK_REGIONS and for the
+ * "physmap" type to %INIT_PHYSMEM_REGIONS.
+ * The :c:func:`memblock_allow_resize` enables automatic resizing of
+ * the region arrays during addition of new regions. This feature
+ * should be used with care so that memory allocated for the region
+ * array will not overlap with areas that should be reserved, for
+ * example initrd.
+ *
+ * The early architecture setup should tell memblock what the physical
+ * memory layout is by using :c:func:`memblock_add` or
+ * :c:func:`memblock_add_node` functions. The first function does not
+ * assign the region to a NUMA node and it is appropriate for UMA
+ * systems. Yet, it is possible to use it on NUMA systems as well and
+ * assign the region to a NUMA node later in the setup process using
+ * :c:func:`memblock_set_node`. The :c:func:`memblock_add_node`
+ * performs such an assignment directly.
+ *
+ * Once memblock is setup the memory can be allocated using either
+ * memblock or bootmem APIs.
+ *
+ * As the system boot progresses, the architecture specific
+ * :c:func:`mem_init` function frees all the memory to the buddy page
+ * allocator.
+ *
+ * If an architecure enables %CONFIG_ARCH_DISCARD_MEMBLOCK, the
+ * memblock data structures will be discarded after the system
+ * initialization compltes.
+ */
+
 static struct memblock_region memblock_memory_init_regions[INIT_MEMBLOCK_REGIONS] __initdata_memblock;
 static struct memblock_region memblock_reserved_init_regions[INIT_MEMBLOCK_REGIONS] __initdata_memblock;
 #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP
-- 
2.7.4


  parent reply	other threads:[~2018-06-30 14:56 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 ` Mike Rapoport [this message]
2018-06-30 14:55 ` [PATCH v2 11/11] docs/mm: add description of boot time memory management Mike Rapoport
2018-07-03 12:23   ` 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

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