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(p200300d82f06a600a397de1d2f8bb66f.dip0.t-ipconnect.de. [2003:d8:2f06:a600:a397:de1d:2f8b:b66f]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-459e6214640sm256183205e9.1.2025.08.11.02.52.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Aug 2025 02:52:12 -0700 (PDT) Message-ID: <112b4bcd-230a-4482-ae2e-67fa22b3596f@redhat.com> Date: Mon, 11 Aug 2025 11:52:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 0/5] add persistent huge zero folio support From: David Hildenbrand To: Kiryl Shutsemau , "Pankaj Raghav (Samsung)" Cc: Suren Baghdasaryan , Ryan Roberts , Baolin Wang , Vlastimil Babka , Zi Yan , Mike Rapoport , Dave Hansen , Michal Hocko , Lorenzo Stoakes , Andrew Morton , Thomas Gleixner , Nico Pache , Dev Jain , "Liam R . Howlett" , Jens Axboe , linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org, Ritesh Harjani , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Darrick J . Wong" , mcgrof@kernel.org, gost.dev@samsung.com, hch@lst.de, Pankaj Raghav References: <20250811084113.647267-1-kernel@pankajraghav.com> 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: tk1fuU23hau4pdnPnqXy3ILdNha1tMa7MJWQr94KWo4_1754905933 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 196BEC0005 X-Stat-Signature: ttjoe8ud6ft8qg6by3psjmi6fzuhr9k3 X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1754905937-930733 X-HE-Meta: U2FsdGVkX18XuxFlM21So2Te92eDJVlNhWhBvBFaKZwg8DkynSQ5uszm3UUrIzcoW2P4SjIo1LMYI1os0etJDDBixzTVEnWCmrcUQAITgLGj0Fuu1YsZHYi8xaG+YSYMzkUlJdNC+v3wC6BW7U1cZ4KOgehJXH7p3gQ3sn2xiI3XsmtZfrMEC+mpo0C7Ul4md7tNtNFVL6CxTUdPW6EcLiNNI15nCiDL1fpXL+4umbLSJslKRgIfkfdkQlO7fJbCMsyv1nHVpotmXDcHvIZUjTJscnLESdeaHdNek4fYmcmyNMFDY7Wehk3/gkHr9AHOtH/5HYff/m167GM4Y5SbLAOe5OOUIZhT6BF+XaYdSm4hBoUW6WSD8U7oFc4Lg+PHvZxl3Fvln2w5n0jvmkOtZyWv7zqZ8RJUlqnuOypENJPx71IZX+krQy4ui1aiwy6W4mKFgsgrUGewKMuk49eO2kRPFeNtaOx6+UcFtYVyriVNh074nuj2CuIju7ALVCCnsUqmgZC8kwD1N9f/6XItKR7Zl8I1Emkzpvn0SOZPOOljqx2biq/3P79YIjJlHSwKWrhG1c6nuDkY8FKMP2BRr0YVuf7HIlEH8g5oNedpESiroDv0a2a4bl74VaUzKkxcSVhbAo1hS2KfpUWVsPToS3qxgMC2pOcEYzImN0Z+bJ/ncC31JBO/RfwvlIx1ZObmCjVHAAWtpwxL2nO51mKi2hsuEKAqEdUjlr63deJWubhIzSXqr+1wsonxYmsK+SJ/qjtNrd2TGMPCMC7apXb9tfa2tmnoz/iz2Kcy7djBEb5Ms8T6Zsr75yG4zKbvKzzcWnG74AMezaN+H8ID13w8w5L6enlq7yznQqvFiOFQoh67J5qb6QdottsP9m9XAKJUuCXLcfE6GXnMtynO4JK2j/Cr73b8NYUjnK7ImdKEuum3ZuQjN7wec++OmmSwzQp3C6ERYiXWRi8ZVYCdqD3 RvQepKZE KDmfg+8EmnVQqRLT41vs0488wUAQSMwMrmoIVWZotfKGMVuKg99K+WKvnQ9Us986a7hIBMk8Yuhjhrl9gSOzR+nkF8c6x+dKH/gM3KB7qkfmMFWibPZdHsgoIOQCkF3kRghVS9pZIJn9lxHnzATL2jaOAT1GQlRVPC0eKw8Wh0/mEsTj23WX8IVfpmASKtI978xnHw4ncpuZuD+7ROkNB1YR+fiqg0v1b+a4yiM0ZbxlE9gArY+MIXm8ne0eF6bZjHPm3MRXO9gFo2MKPrQhSeCeOrLkKfSp/VdUjohGBXFb5JbmjBMHK1iYm275EU9mdKCMbnPyuvCVQbtE8bkrC4wWedhbU9UHQ7uteweuBmneZ8QcNTTApNrTFrzUBp/Cg8TnEpOPvNJt2ueMzq32GLU5eDlvLOiz7twEAo6+X5bJsdL1aarEBHGu0KUyf0VwW79dakEbgjQXzaB7S2qc2Hu4b96CxNa8ETrymrdjoFkPFJJnTbNNaaBrdMljvlkBl4mUzsPE5qzK2Dx0OHUXsLD3YbbGOpj4CXUa9OfuFgR9svlbKiHSTWDrHXg== 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 11:49, David Hildenbrand wrote: > 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. Sorry, RFC v2 I think. It got a bit confusing with series names/versions. -- Cheers, David / dhildenb