+ mm-numa_emu-add-document-for-numa-emulation.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: numa_emu: add document for NUMA emulation
has been added to the -mm mm-new branch.  Its filename is
     mm-numa_emu-add-document-for-numa-emulation.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-numa_emu-add-document-for-numa-emulation.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: Akinobu Mita <akinobu.mita@gmail.com>
Subject: mm: numa_emu: add document for NUMA emulation
Date: Thu, 8 Jan 2026 19:15:34 +0900

Add a document with a brief explanation of numa emulation and how to use
the newly added "numa_emulation.adistance=" kernel cmdline parameter.

Link: https://lkml.kernel.org/r/20260108101535.50696-3-akinobu.mita@gmail.com
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/mm/index.rst          |    1 
 Documentation/mm/numa_emulation.rst |   30 ++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

--- a/Documentation/mm/index.rst~mm-numa_emu-add-document-for-numa-emulation
+++ a/Documentation/mm/index.rst
@@ -24,6 +24,7 @@ see the :doc:`admin guide <../admin-guid
    page_cache
    shmfs
    oom
+   numa_emulation
 
 Unsorted Documentation
 ======================
diff --git a/Documentation/mm/numa_emulation.rst a/Documentation/mm/numa_emulation.rst
new file mode 100644
--- /dev/null
+++ a/Documentation/mm/numa_emulation.rst
@@ -0,0 +1,30 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============
+NUMA emulation
+==============
+
+If CONFIG_NUMA_EMU is enabled, you can create fake NUMA nodes with
+``numa=fake=`` kernel cmdline option.
+See Documentation/admin-guide/kernel-parameters.txt and
+Documentation/arch/x86/x86_64/fake-numa-for-cpusets.rst for more information.
+
+
+Multiple Memory Tiers Creation
+==============================
+
+The "numa_emulation.adistance=" kernel cmdline option allows you to set
+the abstract distance for each NUMA node.
+
+For example, you can create two fake nodes, each in a different memory
+tier by booting with "numa=fake=2 numa_emulation.adistance=576,704".
+Here, the abstract distances of node0 and node1 are set to 576 and 706,
+respectively.
+
+Each memory tier covers an abstract distance chunk size of 128. Thus,
+nodes with abstract distances between 512 and 639 are classified into the
+same memory tier, and nodes with abstract distances between 640 and 767
+are classified into the next slower memory tier.
+
+The abstract distance of fake nodes not specified in the parameter will
+be the default DRAM abstract distance of 576.
_

Patches currently in -mm which might be from akinobu.mita@gmail.com are

mm-memory-tiers-numa_emu-enable-to-create-memory-tiers-using-fake-numa-nodes.patch
mm-numa_emu-add-document-for-numa-emulation.patch
mm-vmscan-dont-demote-if-there-is-not-enough-free-memory-in-the-lower-memory-tier.patch