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(p200300d82f004000a43815411da1723a.dip0.t-ipconnect.de. [2003:d8:2f00:4000:a438:1541:1da1:723a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-458691b2b36sm15638745e9.34.2025.07.23.01.45.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Jul 2025 01:45:58 -0700 (PDT) Message-ID: Date: Wed, 23 Jul 2025 10:45:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 0/4] add static huge zero folio support To: "Pankaj Raghav (Samsung)" , Suren Baghdasaryan , Ryan Roberts , Mike Rapoport , Michal Hocko , Thomas Gleixner , Nico Pache , Dev Jain , Baolin Wang , Borislav Petkov , Ingo Molnar , "H . Peter Anvin" , Vlastimil Babka , Zi Yan , Dave Hansen , Lorenzo Stoakes , Andrew Morton , "Liam R . Howlett" , Jens Axboe Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org, x86@kernel.org, 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: <20250722094215.448132-1-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: <20250722094215.448132-1-kernel@pankajraghav.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: AHfwIgWc98-MRNiiR5J9-6ZQuCD5cMZIlZrLwntRXQw_1753260360 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: ukiz9u4h5t3nxdf6on3r3khhjfsnsn38 X-Rspamd-Queue-Id: A5157140010 X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1753260364-981662 X-HE-Meta: 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 2k7Vfa4E 5YGflZxkc9Pp+fM7YiOX5ndsuMbhUezP5hLE9NiZ36D+uZH1TFBnIgwuT9aiOWnbEfb0FknBGBm6oGkpH1bzoRdAs7QasCBD0josFGuHA5hD1fMwFHdy8tNXiAgnmj3IaiQD2k7Lx5fGQq/H6RQ0FJ2ki9bOSgPKj1OH+nWxxE9YaU4NQgAGbnSlw/SAADlpEnuuduSc+ycryAyCnEuAIYGUq/HAyg4v8eTBxn7raCDX1H0XXMSchuKs2HM4AoP4EAsdgYQ/LtoML2B6zYsDV+hvsDP0YlfafIYDEgXEgrAmV7kUTxbb15pSfYGWxsSmkoMZTRSGrOpJ/ZZQvCIwvCjIdtFQLk81fppIN+TtWpJlzl1MOktQ2PsLWelJ16rniN+tORuY1nBnW34YlMdFwI7bPrWbcbNvtWXMUOVKQmNwpwmlzdjeCzse22JJslqiG62q6Mx56gxy1Z6wENuuWUZCHomNc7Sy9ylAwaKG5T2cuJfs= 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 22.07.25 11:42, Pankaj Raghav (Samsung) wrote: > From: Pankaj Raghav > > NOTE: I am resending as an RFC again based on Lorenzo's feedback. The > old series can be found here [1]. > > There are many places in the kernel where we need to zeroout larger > chunks but the maximum segment we can zeroout 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 we > attach multiple ZERO_PAGEs 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 a 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 STATIC_HUGE_ZERO_FOLIO that will always allocate > the huge_zero_folio, and it will never drop the reference. 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 static huge_zero_folio. > > I will send patches to individual subsystems using the huge_zero_folio > once this gets upstreamed. > > Looking forward to some feedback. Please run scripts/checkpatch.pl on your patches. There are quite some warning for patch #2 and #3, in particular, around using spaces vs. tabs. -- Cheers, David / dhildenb