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(p200300d82f4cdf00a9f5b75b033ca17f.dip0.t-ipconnect.de. [2003:d8:2f4c:df00:a9f5:b75b:33c:a17f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b61ca48719sm10064791f8f.47.2025.07.21.03.10.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Jul 2025 03:10:37 -0700 (PDT) Message-ID: <5dffdbca-c576-489c-b84a-ec2747cfbc21@redhat.com> Date: Mon, 21 Jul 2025 12:10:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH POC] prctl: extend PR_SET_THP_DISABLE to optionally exclude VM_HUGEPAGE To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, Jonathan Corbet , Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Usama Arif , SeongJae Park , Jann Horn , Yafang Shao , Matthew Wilcox References: <20250721090942.274650-1-david@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: <20250721090942.274650-1-david@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: O8Owekt_EKwtiHxqHta7M3Xmz-1tHQ_Rq1Mb3fKq_UQ_1753092638 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: rspam04 X-Rspamd-Queue-Id: B8D382000E X-Stat-Signature: m765k4jrunoimq5ygke64c8zu43c9g5k X-HE-Tag: 1753092643-978670 X-HE-Meta: U2FsdGVkX190GxVbyeTapUMIlN19DdE+98Gcxm/IR5QhAhqNoF6yxnQmSqi3AV33V9f1rBCYCgKcIbaZBKy8DGuEG7OprO8MSXVMPzvNS9biSa/ZxxM9MeyqSKV6teNHFeCS/5NjtC1zXE/LhugeO4mJf0LrOmrrZdb3/lDSLWA3wax9Y4CSDQ4Ti1KGNNLMgnjGnNnvjCEzfhpzho4gcanSlZElvbMg5zS9Yv9QNydBEqajqfMAyvNjLYxX2FZZ18G+L+kNOiNLrn3kUqVF9th5TUqBycAt/UrFm3CSEc7RJRK9Z2BxPnq4Sdkxx0xrybspOwIAzvVmswb78OBUALtb1o7nBM/RyXgeFqgpYNUgU1h8QeHomLELyo7TJxg1drBQ4pEp5dvMg+hk1MbtcsHboPMqMBiFjS5Qjv2dDiX1rrHBhujM1bCvFn+Y/B9RkRogz3Gv0FmiDzZg/VQI+QGYV3/YKnVIZpiisR8plBAhLnGbsR2Lfz+sTE0EnBMa2ct+VvF5pKyma3v33mDtd/FU1P9UgcJRDbnNsRXK+m75GFerxOW7Adt2ev0S5ejPczGuONCeTSeiXTvUdcVaiG41jwMZR6JWpMQ1F35I1ojXRcqQHRXaogVdPtaxku5QLQ3NFu5OTOlzv/OK1Z19ftktfs+cH7sLvRV4VVMdxhENjhHPXRjQPI3durWB5tEwX/eaSYwe5NHTYb/qkTcejHM7h56UQrOdIwel7HM1pZiQBJ0ww+hu3xfSpdQQ7cpPCuRBHI/5LF6Sj0A5f/sGs9yHpyZmhys6Nit35zNC4SPOFDsqNhYvYj1dTnKeQvoBOth1dAqW2edsNEso0SfZFM/xPCOAEWGYdDTJF7zBgwut8jPdawSKQDEKJDCOKJzfWp29M47TLDfH30dUXyLprHWoNtwC5bGfPA0HuFfBZ/nA3JT0KAsCeH+P4I9+Ct9abltUmc2FNhem4+IlUFv WW5jo0+V 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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: Two additions: > > (E) Indicates "THP_enabled: 0" in /proc/pid/status only if THPs are not > disabled completely As raised off-list, this should be "only if THPs are disabled completely" > > Only indicating that THPs are disabled when they are really disabled > completely, not only partially. > > The documented semantics in the man page for PR_SET_THP_DISABLE > "is inherited by a child created via fork(2) and is preserved across > execve(2)" is maintained. This behavior, for example, allows for > disabling THPs for a workload through the launching process (e.g., > systemd where we fork() a helper process to then exec()). > > There is currently not way to prevent that a process will not issue > PR_SET_THP_DISABLE itself to re-enable THP. We could add a "seal" option > to PR_SET_THP_DISABLE through another flag if ever required. The known > users (such as redis) really use PR_SET_THP_DISABLE to disable THPs, so > that is not added for now. I don't think there is any user that would try re-enabling THPs through that interface. It's kind-of against the original purpose (man page): "Setting this flag provides a method for disabling transparent huge pages for jobs where the code cannot be modified ..." So if ever really required, one could investigate forbidding re-enabling once disabled. But that obviously needs more investigation. (also, if a workload ever enables THPs through that mechanism, probably it is to blame) -- Cheers, David / dhildenb