The patch titled
Subject: docs: remove description of DISCONTIGMEM
has been added to the -mm tree. Its filename is
docs-remove-description-of-discontigmem.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/docs-remove-description-of-discontigmem.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/docs-remove-description-of-discontigmem.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Subject: docs: remove description of DISCONTIGMEM
Remove description of DISCONTIGMEM from the "Memory Models" document and
update VM sysctl description so that it won't mention DISCONIGMEM.
Link: https://lkml.kernel.org/r/20210608091316.3622-8-rppt@xxxxxxxxxx
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/sysctl/vm.rst | 12 ++---
Documentation/vm/memory-model.rst | 45 ----------------------
2 files changed, 8 insertions(+), 49 deletions(-)
--- a/Documentation/admin-guide/sysctl/vm.rst~docs-remove-description-of-discontigmem
+++ a/Documentation/admin-guide/sysctl/vm.rst
@@ -938,12 +938,12 @@ allocations, THP and hugetlbfs pages.
To make it sensible with respect to the watermark_scale_factor
parameter, the unit is in fractions of 10,000. The default value of
-15,000 on !DISCONTIGMEM configurations means that up to 150% of the high
-watermark will be reclaimed in the event of a pageblock being mixed due
-to fragmentation. The level of reclaim is determined by the number of
-fragmentation events that occurred in the recent past. If this value is
-smaller than a pageblock then a pageblocks worth of pages will be reclaimed
-(e.g. 2MB on 64-bit x86). A boost factor of 0 will disable the feature.
+15,000 means that up to 150% of the high watermark will be reclaimed in the
+event of a pageblock being mixed due to fragmentation. The level of reclaim
+is determined by the number of fragmentation events that occurred in the
+recent past. If this value is smaller than a pageblock then a pageblocks
+worth of pages will be reclaimed (e.g. 2MB on 64-bit x86). A boost factor
+of 0 will disable the feature.
watermark_scale_factor
--- a/Documentation/vm/memory-model.rst~docs-remove-description-of-discontigmem
+++ a/Documentation/vm/memory-model.rst
@@ -14,15 +14,11 @@ for the CPU. Then there could be several
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`
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
=========
_
Patches currently in -mm which might be from rppt@xxxxxxxxxxxxx are
mm-mmzoneh-simplify-is_highmem_idx.patch
alpha-remove-discontigmem-and-numa.patch
arc-update-comment-about-highmem-implementation.patch
arc-remove-support-for-discontigmem.patch
m68k-remove-support-for-discontigmem.patch
mm-remove-config_discontigmem.patch
arch-mm-remove-stale-mentions-of-disconigmem.patch
docs-remove-description-of-discontigmem.patch
mm-replace-config_need_multiple_nodes-with-config_numa.patch
mm-replace-config_flat_node_mem_map-with-config_flatmem.patch
docs-procrst-meminfo-briefly-describe-gaps-in-memory-accounting.patch
include-linux-mmzoneh-add-documentation-for-pfn_valid.patch
memblock-update-initialization-of-reserved-pages.patch
arm64-decouple-check-whether-pfn-is-in-linear-map-from-pfn_valid.patch
arm64-drop-pfn_valid_within-and-simplify-pfn_valid.patch
mmap-make-mlock_future_check-global.patch
riscv-kconfig-make-direct-map-manipulation-options-depend-on-mmu.patch
set_memory-allow-querying-whether-set_direct_map_-is-actually-enabled.patch
mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas.patch
pm-hibernate-disable-when-there-are-active-secretmem-users.patch
arch-mm-wire-up-memfd_secret-system-call-where-relevant.patch
secretmem-test-add-basic-selftest-for-memfd_secret2.patch
