Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> --- 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 + * 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 -- 2.7.4
