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Wong" , mcgrof@kernel.org, gost.dev@samsung.com, hch@lst.de, Pankaj Raghav References: <20250811084113.647267-1-kernel@pankajraghav.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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: NDIN1fY0G9W7ViNT2xIcVYLGFgzO87Bdx6tKqTN3o5s_1754905763 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: 8e3gsjieu5goih73uit7a3984gdno889 X-Rspamd-Queue-Id: B411D40008 X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1754905766-527109 X-HE-Meta: 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 CeuMFB0F 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 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 11.08.25 11:43, Kiryl Shutsemau wrote: > On Mon, Aug 11, 2025 at 10:41:08AM +0200, Pankaj Raghav (Samsung) wrote: >> From: Pankaj Raghav >> >> Many places in the kernel need to zero out larger chunks, but the >> maximum segment we can zero out at a time by ZERO_PAGE is limited by >> PAGE_SIZE. >> >> This concern was raised during the review of adding Large Block Size support >> to XFS[2][3]. >> >> This is especially annoying in block devices and filesystems where >> multiple ZERO_PAGEs are attached to the bio in different bvecs. With multipage >> bvec support in block layer, it is much more efficient to send out >> larger zero pages as a part of single bvec. >> >> Some examples of places in the kernel where this could be useful: >> - blkdev_issue_zero_pages() >> - iomap_dio_zero() >> - vmalloc.c:zero_iter() >> - rxperf_process_call() >> - fscrypt_zeroout_range_inline_crypt() >> - bch2_checksum_update() >> ... >> >> Usually huge_zero_folio is allocated on demand, and it will be >> deallocated by the shrinker if there are no users of it left. At the moment, >> huge_zero_folio infrastructure refcount is tied to the process lifetime >> that created it. This might not work for bio layer as the completions >> can be async and the process that created the huge_zero_folio might no >> longer be alive. And, one of the main point that came during discussion >> is to have something bigger than zero page as a drop-in replacement. >> >> Add a config option PERSISTENT_HUGE_ZERO_FOLIO that will always allocate >> the huge_zero_folio, and disable the shrinker so that huge_zero_folio is >> never freed. >> This makes using the huge_zero_folio without having to pass any mm struct and does >> not tie the lifetime of the zero folio to anything, making it a drop-in >> replacement for ZERO_PAGE. >> >> I have converted blkdev_issue_zero_pages() as an example as a part of >> this series. I also noticed close to 4% performance improvement just by >> replacing ZERO_PAGE with persistent huge_zero_folio. >> >> I will send patches to individual subsystems using the huge_zero_folio >> once this gets upstreamed. >> >> Looking forward to some feedback. > > Why does it need to be compile-time? Maybe whoever needs huge zero page > would just call get_huge_zero_page()/folio() on initialization to get it > pinned? That's what v2 did, and this way here is cleaner. -- Cheers, David / dhildenb