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Sun, 21 Dec 2025 16:49:24 -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 Subject: [PATCH v2 2/3] mm: numa_emu: add document for NUMA emulation Date: Mon, 22 Dec 2025 09:48:33 +0900 Message-ID: <20251222004834.10539-3-akinobu.mita@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251222004834.10539-1-akinobu.mita@gmail.com> References: <20251222004834.10539-1-akinobu.mita@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D5BB640009 X-Stat-Signature: wsttkxx5m4cyitch5op9ry71w3ap5oe5 X-Rspam-User: X-HE-Tag: 1766364565-718718 X-HE-Meta: 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 6wkxp15d rYTM5NwSs0IGDvFJ/45zNmLMeJv9anpDHB+lT7W3ECjs4yTnWjXAKxTiU4ZjVmFx35G8KVUtosn656mjTX8CnrkbHJf4QlPCXPM+8ACSp01vWmEn2HYlljwHybOkx8KCSl+FifyClKe12suFgR+AEZm5hhMuV/zIGZ07CB0AUxI/QfRO/o6I2nM4fRDbRC58DVStIaXgWJgqj5bV1+IBvCAnIc9ERAjFBFcxluAgmuJaP2xdkbzUkpNgw7jtI2Rf9XJ31Tfd6vTLluEJ7RdeCAOScX8qf0aarrP+un8XlhLU2Tuo= 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 --- New 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