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(p200300d82f1f36000dc826ee9aa9fdc7.dip0.t-ipconnect.de. [2003:d8:2f1f:3600:dc8:26ee:9aa9:fdc7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b5e8dc91d8sm20291948f8f.42.2025.07.17.04.46.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 17 Jul 2025 04:46:04 -0700 (PDT) Message-ID: Date: Thu, 17 Jul 2025 13:46:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/5] mm: add static PMD zero page To: "Pankaj Raghav (Samsung)" Cc: Suren Baghdasaryan , Ryan Roberts , Baolin Wang , Borislav Petkov , Ingo Molnar , "H . Peter Anvin" , 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, willy@infradead.org, linux-mm@kvack.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: <20250707142319.319642-1-kernel@pankajraghav.com> <20250707142319.319642-4-kernel@pankajraghav.com> <26fded53-b79d-4538-bc56-3d2055eb5d62@redhat.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: cgL8Vf5zwHr7V_Sg7R_foh8pMX1Ge35O8J3XlLyqcqs_1752752766 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 7A67A14000F X-Stat-Signature: w6ij8b96afkn6r16a99rpzf445eamhtq X-HE-Tag: 1752752769-346240 X-HE-Meta: U2FsdGVkX19CKuJ8DLjGhkePnjMMcHM30II/Ry/Cdz1fmJjQaFNrOtzLQARPTseK4KuM3uHtgItUmhe0R+GfBffpLK+0jutwJD0BMMZG5jBwE7K9Ol9SMTU+Cyc6MPUIaZw7qynW+uJRqjK4OLXFgo3wQPMGfKSntvAZuz+aGYZ0BvlIBYqD//e8Kv/FRMSSe8lxqy+waX2v2L9fdX6T4D1ljqSgzEj1MbUEnRJXKdq+EVwB+98aGo2js2+ig1iv5/g6PxKMmKx1q9amYiiDXBVRx+EX8ai6RYgyoP6shz8lP/EhJHweite739v0mua4LwrSk6yXY3j4Jx55UL7jwLM+Tl5e92YQ6y17QuWQn2q2GsVQpA+Tgt4XvKd3fMv2TmSxjT9H6cLhV2ZhN3qBjNMEwSgdV1ExxSmMxZmoXWIQg23K9IU5x1kjUQRK1giorHNg8MkSl39Hc1IG/omVbKlBudY+4i4kRB9/8u5sg1rhqjc2v6B9kivdoA0Yz6+D5nf9bJxfGsYT7yo7sCWuRsWy32IH4/Zu0KJv16U+4RZP5Le8aOcSMr+jSj9tps04yIFe5ZQtFvMAuSbukxpo4rAMNwU1sTS6Bc2LTF7GJJUSTg14/KLFv8EMjXPcPw4R7+gszqRa34XoN8OQRM6GSMkh4OtVdXrcS8MKoD12ttMRm5yLIAurfZwLelCrPZaW3Q+qu3Zd2doG8KAXkULWuQC9MI9Eacbtjl2HHw5mzLvvpwQC8OpywpINcdAUZVTOCyW8uG0PyrC0GDfbHliHpP6dPTVpzD17LCzDqqq3uyUEjVtCuVkLg/ZjbtI7wnm+xq9ZxwPhEtM/hjvca5cc7NuUYbHSMLg0K82hMxasskXCQA1ChAWtQOZS/FG7e9j80Mh+X5MD8hU6xPMgQwb67W61vYj0K6/6iXryGLTHzlfRasE0wIXdaAPVj3xt+Isy9GB6mUSQBnJDINfmkKv Ln3tHOSC 7ef78HvHftEaiduZrLQT1K6Rd3QRonfXGTj211dPmVMOaq9gYkpeMDjyLCzPjJmNyBLsQgUkG8XvwxVaq/qPp/qzsv9aWix6quu8b2cpA1tLpqwvMAclq+v43ERmJNKpjRraozdWG5tiZqrP0IzRulmfkZv0OmEOthLj31RaOD2p0cnWCNJn/ESC8Mwkp3g5/+pyPPkstDatwvuGYiJL2+yqjzG2bom+NVz/2owIhbNWuUbIyl+nKfxg6Ob0NilafQZDXW0y9wAlSxmBK+ME9WahCFdqeELAnDKxWxfKp7O7flKmI4KhN5G5BxB0iyK1sHCqOexF3/CaSRwMzC9yCwO5+bQsr3ieibq+7rp28wvG9jeyCnEyOoxr0mysOILXxChOizA2Y/IY5LMzsxy3oIuRv2IkR10YWP0lgDayP7vy3ts8DLXLVcQOB9E9r8fLMPVsLY6BD3eeTv4g0zujoQvI48A== 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 17.07.25 12:34, Pankaj Raghav (Samsung) wrote: >>> Then, we'd only need a config option to allow for that to happen. >> >> Something incomplete and very hacky just to give an idea. It would try allocating >> it if there is actual code running that would need it, and then have it >> stick around forever. >> > Thanks a lot for this David :) I think this is a much better idea and > reduces the amount code and reuse the existing infrastructure. > > I will try this approach in the next version. > > >> + /* >> + * Our raised reference will prevent the shrinker from ever having >> + * success -> static. >> + */ >> + if (atomic_read(&huge_zero_folio_is_static)) >> + return huge_zero_folio; >> + /* TODO: memblock allocation if buddy is not up yet? Or Reject that earlier. */ > > Do we need memblock allocation? At least the use cases I forsee for > static pmd zero page are all after the mm is up. So I don't see why we > need to allocate it via memblock. Even better! We might want to detect whether allocation of the huge zeropage failed a couple of times and then just give up. Otherwise, each and every user of the largest zero folio will keep allocating it. -- Cheers, David / dhildenb