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author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-06-29 17:29:11 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-06-29 17:29:11 -0700 |
commit | 65090f30ab791810a3dc840317e57df05018559c (patch) | |
tree | f417526656da37109777e89613e140ffc59228bc /Documentation/vm | |
parent | 349a2d52ffe59b7a0c5876fa7ee9f3eaf188b830 (diff) | |
parent | 0ed950d1f28142ccd9a9453c60df87853530d778 (diff) |
Merge branch 'akpm' (patches from Andrew)
Merge misc updates from Andrew Morton:
"191 patches.
Subsystems affected by this patch series: kthread, ia64, scripts,
ntfs, squashfs, ocfs2, kernel/watchdog, and mm (gup, pagealloc, slab,
slub, kmemleak, dax, debug, pagecache, gup, swap, memcg, pagemap,
mprotect, bootmem, dma, tracing, vmalloc, kasan, initialization,
pagealloc, and memory-failure)"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (191 commits)
mm,hwpoison: make get_hwpoison_page() call get_any_page()
mm,hwpoison: send SIGBUS with error virutal address
mm/page_alloc: split pcp->high across all online CPUs for cpuless nodes
mm/page_alloc: allow high-order pages to be stored on the per-cpu lists
mm: replace CONFIG_FLAT_NODE_MEM_MAP with CONFIG_FLATMEM
mm: replace CONFIG_NEED_MULTIPLE_NODES with CONFIG_NUMA
docs: remove description of DISCONTIGMEM
arch, mm: remove stale mentions of DISCONIGMEM
mm: remove CONFIG_DISCONTIGMEM
m68k: remove support for DISCONTIGMEM
arc: remove support for DISCONTIGMEM
arc: update comment about HIGHMEM implementation
alpha: remove DISCONTIGMEM and NUMA
mm/page_alloc: move free_the_page
mm/page_alloc: fix counting of managed_pages
mm/page_alloc: improve memmap_pages dbg msg
mm: drop SECTION_SHIFT in code comments
mm/page_alloc: introduce vm.percpu_pagelist_high_fraction
mm/page_alloc: limit the number of pages on PCP lists when reclaim is active
mm/page_alloc: scale the number of pages that are batch freed
...
Diffstat (limited to 'Documentation/vm')
-rw-r--r-- | Documentation/vm/memory-model.rst | 45 |
1 files changed, 2 insertions, 43 deletions
diff --git a/Documentation/vm/memory-model.rst b/Documentation/vm/memory-model.rst index ce398a7dc6cd..30e8fbed6914 100644 --- a/Documentation/vm/memory-model.rst +++ b/Documentation/vm/memory-model.rst @@ -14,15 +14,11 @@ for the CPU. Then there could be several contiguous ranges at completely distinct addresses. And, don't forget about NUMA, where different memory banks are attached to different CPUs. -Linux abstracts this diversity using one of the three memory models: -FLATMEM, DISCONTIGMEM and SPARSEMEM. Each architecture defines what +Linux abstracts this diversity using one of the two memory models: +FLATMEM and SPARSEMEM. Each architecture defines what memory models it supports, what the default memory model is and whether it is possible to manually override that default. -.. note:: - At time of this writing, DISCONTIGMEM is considered deprecated, - although it is still in use by several architectures. - All the memory models track the status of physical page frames using struct page arranged in one or more arrays. @@ -63,43 +59,6 @@ straightforward: `PFN - ARCH_PFN_OFFSET` is an index to the The `ARCH_PFN_OFFSET` defines the first page frame number for systems with physical memory starting at address different from 0. -DISCONTIGMEM -============ - -The DISCONTIGMEM model treats the physical memory as a collection of -`nodes` similarly to how Linux NUMA support does. For each node Linux -constructs an independent memory management subsystem represented by -`struct pglist_data` (or `pg_data_t` for short). Among other -things, `pg_data_t` holds the `node_mem_map` array that maps -physical pages belonging to that node. The `node_start_pfn` field of -`pg_data_t` is the number of the first page frame belonging to that -node. - -The architecture setup code should call :c:func:`free_area_init_node` for -each node in the system to initialize the `pg_data_t` object and its -`node_mem_map`. - -Every `node_mem_map` behaves exactly as FLATMEM's `mem_map` - -every physical page frame in a node has a `struct page` entry in the -`node_mem_map` array. When DISCONTIGMEM is enabled, a portion of the -`flags` field of the `struct page` encodes the node number of the -node hosting that page. - -The conversion between a PFN and the `struct page` in the -DISCONTIGMEM model became slightly more complex as it has to determine -which node hosts the physical page and which `pg_data_t` object -holds the `struct page`. - -Architectures that support DISCONTIGMEM provide :c:func:`pfn_to_nid` -to convert PFN to the node number. The opposite conversion helper -:c:func:`page_to_nid` is generic as it uses the node number encoded in -page->flags. - -Once the node number is known, the PFN can be used to index -appropriate `node_mem_map` array to access the `struct page` and -the offset of the `struct page` from the `node_mem_map` plus -`node_start_pfn` is the PFN of that page. - SPARSEMEM ========= |