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[2003:d8:2f03:5b00:f549:a879:b2d3:73ee]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a4efe5b96fsm4168233f8f.8.2025.05.30.01.52.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 May 2025 01:52:46 -0700 (PDT) Message-ID: <9c920642-228b-4eb0-920a-269473ea824e@redhat.com> Date: Fri, 30 May 2025 10:52:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] fix MADV_COLLAPSE issue if THP settings are disabled To: Lorenzo Stoakes Cc: Ryan Roberts , Baolin Wang , akpm@linux-foundation.org, hughd@google.com, Liam.Howlett@oracle.com, npache@redhat.com, dev.jain@arm.com, ziy@nvidia.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <05d60e72-3113-41f0-b81f-225397f06c81@arm.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: _Db61alMGLCGG2woTQ7cGZA0e2n5TwjtxONIlBimlcA_1748595168 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: E393CC0007 X-Stat-Signature: r863uazqord48coxktzbs4aa1ztzikd6 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1748595170-70544 X-HE-Meta: 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 JIE9wFo4 p/BDH080zP+TeIRVHQfYfSjcfrjyddlXq2oZSfZL4CM9c/xTuh4FBh5H93HUrey5gl4Ktcg3ECVkvHyMAAg1h7npwfhwK82OkJDf64B7lSdGYEGVylVFEkXcAqvAQJpwMB0rxDLMCbgM0xIogfBE4Obx8Pnp5k1DtEWkjLX0LbEcA3hb1Rtj5McYzpBG6Gn/kfHWmdkbYHyYLEEFsHEkslg5IkVaqhSV5wmjgoxr4drpNLEP/0Pcp2JWaJt4TqT2QmqbPgvzcqXCxRpOyDmNsp5JTssFpVqiyOb6Aq7FlS97G5ofNXys1X15LnNPkRGU8maVIzbRcg0gyea65RaxLAHfKTyf6GTuwc4Z81LWW4H/vhkLGBQ1c9W4b9fGxAplFOvQlT6QsX57PZAgwHxYMaH+fgdi7MlUCwKdMUczgsq/BP6Epuj42lAZKJtyW6Ry0ipxqtiVRgD5Y3Gc= 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 30.05.25 10:47, Lorenzo Stoakes wrote: > On Fri, May 30, 2025 at 10:44:36AM +0200, David Hildenbrand wrote: >> On 30.05.25 10:04, Ryan Roberts wrote: >>> On 29/05/2025 09:23, Baolin Wang wrote: >>>> As we discussed in the previous thread [1], the MADV_COLLAPSE will ignore >>>> the system-wide anon/shmem THP sysfs settings, which means that even though >>>> we have disabled the anon/shmem THP configuration, MADV_COLLAPSE will still >>>> attempt to collapse into a anon/shmem THP. This violates the rule we have >>>> agreed upon: never means never. This patch set will address this issue. >>> >>> This is a drive-by comment from me without having the previous context, but... >>> >>> Surely MADV_COLLAPSE *should* ignore the THP sysfs settings? It's a deliberate >>> user-initiated, synchonous request to use huge pages for a range of memory. >>> There is nothing *transparent* about it, it just happens to be implemented using >>> the same logic that THP uses. >>> >>> I always thought this was a deliberate design decision. >> >> If the admin said "never", then why should a user be able to overwrite that? >> >> The design decision I recall is that if VM_NOHUGEPAGE is set, we'll ignore >> that. Because that was set by the app itself (MADV_NOHUEPAGE). >> > > I'm with David on this one. > > I think it's principal of least surprise - to me 'never' is pretty > emphatic, and keep in mind the other choices are 'always' and... 'madvise' > :) which explicitly is 'hey only do this if madvise tells you to'. > > I'd be rather surprised if I hadn't set madvise and a user uses madvise to > in some fashion override the never. > > I mean I think we all agree this interface is to use a technical term - > crap - and we need something a lot more fine-grained and smart, but I think > given the situation we're in we should make it at least as least surprising > as possible. Yes. If you configure "never" you are supposed to suffer, consistently. -- Cheers, David / dhildenb