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Wysocki" , Len Brown , Andrew Morton , Dave Jiang , Dan Williams , Jonathan Cameron , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Ho-Ren (Jack) Chuang" , "Ho-Ren (Jack) Chuang" , linux-cxl@vger.kernel.org, qemu-devel@nongnu.org Subject: Re: [PATCH v1 0/1] Improved Memory Tier Creation for CPUless NUMA Nodes In-Reply-To: <20240301082248.3456086-1-horenchuang@bytedance.com> (Ho-Ren Chuang's message of "Fri, 1 Mar 2024 08:22:44 +0000") References: <20240301082248.3456086-1-horenchuang@bytedance.com> Date: Mon, 04 Mar 2024 10:45:02 +0800 Message-ID: <87frx6btqp.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Queue-Id: 962454000E X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 471uxj5y863a8kqdfod7tgqane58ee18 X-HE-Tag: 1709520423-982785 X-HE-Meta: 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 jyDKLwxK d6pP5uOd3mIOV2L8amFQmxSF6no4cjc3KB6PQR4fb+xNsx2tjHQzThWmyGIv1DT9Pvr7q6HARvKq86BGkEEmCfyy4XxP4yavHLS8twOtLu0RzJIUC1Sk8gLOeQDin1XdXiFFEfl+45BAZ9mBFbn1V2X3fs5S7pvWrKglO2PxeR4hf0c0LX9iGZMQg8o/HBioTfCPfmT6k4Xv2JgV1dTDznzRQ6jznb7Ai96jHLHprXw+gVYNLMDIOoVtqwhqjivWqzrxO42zt7XCGU9OENdLkwUC25saAVRJslukL6GjXvp95d8C5s5G0GM+4v2597W2+dSN+CnBDW+ULQYJo8PmutoScGYkpqfs6YCTeMmiMWGcrJX8= 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: "Ho-Ren (Jack) Chuang" writes: > The memory tiering component in the kernel is functionally useless for > CPUless memory/non-DRAM devices like CXL1.1 type3 memory because the nodes > are lumped together in the DRAM tier. > https://lore.kernel.org/linux-mm/PH0PR08MB7955E9F08CCB64F23963B5C3A860A@PH0PR08MB7955.namprd08.prod.outlook.com/T/ I think that it's unfair to call it "useless". Yes, it doesn't work if the CXL memory device are not enumerate via drivers/dax/kmem.c. So, please be specific about in which cases it doesn't work instead of too general "useless". > This patchset automatically resolves the issues. It delays the initialization > of memory tiers for CPUless NUMA nodes until they obtain HMAT information > at boot time, eliminating the need for user intervention. > If no HMAT specified, it falls back to using `default_dram_type`. > > Example usecase: > We have CXL memory on the host, and we create VMs with a new system memory > device backed by host CXL memory. We inject CXL memory performance attributes > through QEMU, and the guest now sees memory nodes with performance attributes > in HMAT. With this change, we enable the guest kernel to construct > the correct memory tiering for the memory nodes. > > Ho-Ren (Jack) Chuang (1): > memory tier: acpi/hmat: create CPUless memory tiers after obtaining > HMAT info > > drivers/acpi/numa/hmat.c | 3 ++ > include/linux/memory-tiers.h | 6 +++ > mm/memory-tiers.c | 76 ++++++++++++++++++++++++++++++++---- > 3 files changed, 77 insertions(+), 8 deletions(-) -- Best Regards, Huang, Ying