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Thu, 08 Jan 2026 02:16:30 -0800 (PST) From: Akinobu Mita To: akinobu.mita@gmail.com Cc: linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hannes@cmpxchg.org, david@kernel.org, mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, bingjiao@google.com Subject: [PATCH v3 2/3] mm: numa_emu: add document for NUMA emulation Date: Thu, 8 Jan 2026 19:15:34 +0900 Message-ID: <20260108101535.50696-3-akinobu.mita@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260108101535.50696-1-akinobu.mita@gmail.com> References: <20260108101535.50696-1-akinobu.mita@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 595E218000F X-Rspamd-Server: rspam10 X-Stat-Signature: ppt4errzyqzp559jw473xh3quqpn1pz5 X-HE-Tag: 1767867392-19057 X-HE-Meta: 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 yYKv125Y oJ5W01BKO4ENb9vl1AxcZ4i009Iz3Oa+MWVc2G2Ln7H+z1kndsKOJ0VxfpHNLxXSqxwY+cJMsB86SN0/DmIW3iUz5zDnD1dPt0pAos1EPl0stgpb1qZZKeHYJWyxk/jjsSd1dkyhHunRGO6+5JlZJA/mf1bcu01Fkyz3UVMfexAsGWj66X9rMQ/V6EB5ZBmJPCiUWY77fUs5x0AVsiOJsywSEyFGNZQ+xvFZ6D/AQbGlp8ZSUjbo4s9ApaFPqL66fDGYBXERcmMmFlrW2Mc4jGsXiZxNpKPkkeVPO2XmVeuR3ru0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Add a document with a brief explanation of numa emulation and how to use the newly added "numa_emulation.adistance=" kernel cmdline parameter. Signed-off-by: Akinobu Mita --- v2: - added in v2 Documentation/mm/index.rst | 1 + Documentation/mm/numa_emulation.rst | 30 +++++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) create mode 100644 Documentation/mm/numa_emulation.rst diff --git a/Documentation/mm/index.rst b/Documentation/mm/index.rst index 7aa2a8886908..7d628edd6a17 100644 --- a/Documentation/mm/index.rst +++ b/Documentation/mm/index.rst @@ -24,6 +24,7 @@ see the :doc:`admin guide <../admin-guide/mm/index>`. page_cache shmfs oom + numa_emulation Unsorted Documentation ====================== diff --git a/Documentation/mm/numa_emulation.rst b/Documentation/mm/numa_emulation.rst new file mode 100644 index 000000000000..dce9f607c031 --- /dev/null +++ b/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. -- 2.43.0