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Howlett" , Yafang Shao , akpm@linux-foundation.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, hannes@cmpxchg.org, usamaarif642@gmail.com, willy@infradead.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org References: <20250520060504.20251-1-laoar.shao@gmail.com> <7d8a9a5c-e0ef-4e36-9e1d-1ef8e853aed4@redhat.com> <3b792576-6189-4f53-b47f-95875181a656@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/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ko93rQqs70DxxZZjL_zlXVA1__DvdfFZ6NZuHwbh7S0_1748291867 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 36455100004 X-Stat-Signature: gxssno48mpfd41we6hmijg969h9r5xp6 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1748291870-514611 X-HE-Meta: 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 jNEuqE7E 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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 26.05.25 22:30, Gutierrez Asier wrote: > > > On 5/26/2025 7:51 PM, David Hildenbrand wrote: >> On 26.05.25 17:54, Liam R. Howlett wrote: >>> * Liam R. Howlett [250526 10:54]: >>>> * David Hildenbrand [250526 06:49]: >>>>> On 26.05.25 11:37, Yafang Shao wrote: >>>>>> On Mon, May 26, 2025 at 4:14 PM David Hildenbrand wrote: >>>>>>> >>>>>>>> Hi all, >>>>>>>> >>>>>>>> Let’s summarize the current state of the discussion and identify how >>>>>>>> to move forward. >>>>>>>> >>>>>>>> - Global-Only Control is Not Viable >>>>>>>> We all seem to agree that a global-only control for THP is unwise. In >>>>>>>> practice, some workloads benefit from THP while others do not, so a >>>>>>>> one-size-fits-all approach doesn’t work. >>>>>>>> >>>>>>>> - Should We Use "Always" or "Madvise"? >>>>>>>> I suspect no one would choose 'always' in its current state. ;) >>>>>>> >>>>>>> IIRC, RHEL9 has the default set to "always" for a long time. >>>>>> >>>>>> good to know. >>>>>> >>>>>>> >>>>>>> I guess it really depends on how different the workloads are that you >>>>>>> are running on the same machine. >>>>>> >>>>>> Correct. If we want to enable THP for specific workloads without >>>>>> modifying the kernel, we must isolate them on dedicated servers. >>>>>> However, this approach wastes resources and is not an acceptable >>>>>> solution. >>>>>> >>>>>>> >>>>>>>    > Both Lorenzo and David propose relying on the madvise mode. However,> >>>>>>> since madvise is an unprivileged userspace mechanism, any user can >>>>>>>> freely adjust their THP policy. This makes fine-grained control >>>>>>>> impossible without breaking userspace compatibility—an undesirable >>>>>>>> tradeoff. >>>>>>> >>>>>>> If required, we could look into a "sealing" mechanism, that would >>>>>>> essentially lock modification attempts performed by the process (i.e., >>>>>>> MADV_HUGEPAGE). >>>>>> >>>>>> If we don’t introduce a new THP mode and instead rely solely on >>>>>> madvise, the "sealing" mechanism could either violate the intended >>>>>> semantics of madvise(), or simply break madvise() entirely, right? >>>>> >>>>> We would have to be a bit careful, yes. >>>>> >>>>> Errors from MADV_HUGEPAGE/MADV_NOHUGEPAGE are often ignored, because these >>>>> options also fail with -EINVAL on kernels without THP support. >>>>> >>>>> Ignoring MADV_NOHUGEPAGE can be problematic with userfaultfd. >>>>> >>>>> What you likely really want to do is seal when you configured >>>>> MADV_NOHUGEPAGE to be the default, and fail MADV_HUGEPAGE later. >>> >>> I am also not entirely sure how sealing a non-existing vma would work. >>> We'd have to seal the default flags, but sealing is one way and this >>> surely shouldn't be one way? >> >> You probably have  mseal() in mind. Just like we wouldn't be using madvise(), we also wouldn't be using mseal(). >> >> It could be a simple mctrl()/whatever option/flag to set the default and no longer allow changing the default and per-VMA flags, unless CAP_SYS_ADMIN or sth like that. >> > > This isn't really TRANSPARENT Huge Pages, since we will require > the application to determine which memory range will be mapped with > huge pages. Huh? No idea how you concluded that. Can you elaborate? -- Cheers, David / dhildenb