[10/11] docs/mm: memblock: add overview documentation

Commit Message

Mike Rapoport June 18, 2018, 4:59 p.m. UTC

Signed-off-by: Mike Rapoport <[e-mail]>
---
 mm/memblock.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

Comments

Randy Dunlap June 18, 2018, 5:21 p.m. UTC | #1

Hi,

On 06/18/2018 09:59 AM, Mike Rapoport wrote:
> Signed-off-by: Mike Rapoport <[e-mail]>
> ---
>  mm/memblock.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/mm/memblock.c b/mm/memblock.c
> index c4838a9..8bfeb82 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -26,6 +26,61 @@
>  
>  #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 is the

      The early architecture setup should tell memblock what the physical
      memory layout is by using :c:func:`memblock_add` or

> + * physical memory layout 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 approptiate for UMA

                                                 appropriate

> + * 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
> + * intialization compltes

      initialization completes.

> + */
> +
>  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
>

Patch

diff --git a/mm/memblock.c b/mm/memblock.c
index c4838a9..8bfeb82 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -26,6 +26,61 @@ 
 
 #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 is the
+ * physical memory layout 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 approptiate 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
+ * intialization 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