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(p200300d82f0e2c00d6bb8859fbbcb8a9.dip0.t-ipconnect.de. [2003:d8:2f0e:2c00:d6bb:8859:fbbc:b8a9]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-459c58ececdsm45294775e9.1.2025.08.04.12.10.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 Aug 2025 12:10:15 -0700 (PDT) Message-ID: <5bf65002-8d2f-4b9b-8f22-3ba69124335c@redhat.com> Date: Mon, 4 Aug 2025 21:10:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm/page_alloc: Add PCP list for THP CMA To: Zi Yan Cc: Juan Yescas , akash.tyagi@mediatek.com, Andrew Morton , angelogioacchino.delregno@collabora.com, hannes@cmpxchg.org, Brendan Jackman , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, Linux Memory Management List , matthias.bgg@gmail.com, Michal Hocko , Suren Baghdasaryan , Vlastimil Babka , wsd_upstream@mediatek.com, Kalesh Singh , "T.J. Mercier" , Isaac Manjarres References: <8A3D2D44-DCE9-48FC-A684-C43006B3912F@nvidia.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: <8A3D2D44-DCE9-48FC-A684-C43006B3912F@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: p7p4f5D4wJi9QAR8pXGVb_be--FgPeh7HU7uwQkGXIw_1754334616 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: q9dtwfwzt457gx5me8j9bb5erjp916u6 X-Rspamd-Queue-Id: 9D24140010 X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1754334619-795728 X-HE-Meta: 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 tDJhc+9c x6EDwylzwYCt/Nom5cMDEqvBKrH0l/hadRpd6qlukNs/WzPRvy3BYjZKnPhzx+CTqhewauVv3srTHPxFJe5gBUe1H7k6NhRyZvLxvMp8+r/7LulmK+WnOwO7DiywLzuGduSwlmk2YBIJzC0iaa2HS7tPfN3TEvwjOAA5ZflMCXt/3C6gfuqxcKRaZSzpHB9MtUAWH 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: On 04.08.25 21:00, Zi Yan wrote: > On 4 Aug 2025, at 14:49, David Hildenbrand wrote: > >> On 04.08.25 20:20, Juan Yescas wrote: >>> Hi David/Zi, >>> >>> Is there any reason why the MIGRATE_CMA pages are not in the PCP lists? >>> >>> There are many devices that need fast allocation of MIGRATE_CMA pages, >>> and they have to get them from the buddy allocator, which is a bit >>> slower in comparison to the PCP lists. >>> >>> We also have cases where the MIGRATE_CMA memory requirements are big. >>> For example, GPUs need MIGRATE_CMA memory in the ranges of 30MiB to 500MiBs. >>> These cases would benefit if we have THPs for CMAs. >>> >>> Could we add the support for MIGRATE_CMA pages on the PCP and THP lists? >> >> Remember how CMA memory is used: >> >> The owner allocates it through cma_alloc() and friends, where the CMA allocator will try allocating *specific physical memory regions* using alloc_contig_range(). It doesn't just go ahead and pick a random CMA page from the buddy (or PCP) lists. Doesn't work (just imagine having different CMA areas etc). > > Yeah, unless some code is relying on gfp_to_alloc_flags_cma() to get ALLOC_CMA > to try to get CMA pages from buddy. Right, but that's just for internal purposes IIUC, to grab pages from the CMA lists when serving movable allocations. > >> >> Anybody else is free to use CMA pages for MOVABLE allocations. So we treat them as being MOVABLE on the PCP. >> >> Having a separate CMA PCP list doesn't solve or speedup anything, really. > > It can be slower when small CMA pages are on PCP lists and large CMA pages > cannot be allocated, one needs to drain PCP lists. This assumes the code is > trying to get CMA pages from buddy, which is not how CMA memory is designed > to be used like David mentioned above. Right. And alloc_contig_range_noprof() already does a drain_all_pages(cc.zone). -- Cheers, David / dhildenb