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Howlett" , Vlastimil Babka , Harry Yoo , Xu Xin , Chengming Zhou , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Alistair Popple , "Matthew Wilcox (Oracle)" , Christian Brauner , Usama Arif , Yu Zhao , Baolin Wang , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250724084441.380404-1-link@vivo.com> <764c48ad-8869-4f69-898e-0a1c58684f7d@lucifer.local> <40cb7d64-0b90-4561-8e10-06a808a2766a@vivo.com> <87bjp93vb6.fsf@DESKTOP-5N7EMDA> <9a0eade4-8981-4379-8260-e673a1803d56@vivo.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: <9a0eade4-8981-4379-8260-e673a1803d56@vivo.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: hIW3sw00dTsQwDhqnzoy5lRovIPTsZcrx4XVaiWUphY_1753435564 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: 6A7E2C0002 X-Stat-Signature: ka94s6j97jnmk9rkot31ak991tgnzchf X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1753435567-119267 X-HE-Meta: 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 hzAHZcoY 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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: >> If you cannot prove that the optimization has some practical effect, >> it's hard to persuade others for increased complexity. > > To be honest, this patch stems from an issue I noticed during code review. > > When this patchset was completed, I did put in some effort to find its > benefits, and it was only > > under such an exaggeratedly constructed test scenario that the effect > could be demonstrated. :( I mean, thanks for looking into that and trying to find a way to improve it. :) That VMA walk is the real problem, stopping earlier is just an optimization that works in some cases. I guess on average it will improve things, although probably really hard to quantify in reality. I think tracking the #migration entries might be a very good debugging tool. A cleaner and more reliably solution regarding what you tried to implement would be able to (a) track it in a separate counter, at the time we establish/remove a migration entry, not once the mapcount is already 0. With "struct folio" getting allocated separately in the future this could maybe be feasible (and putting it under a config knob). (b) doing it also for large folios as well (b) might be tricky with migration entries being used for THP splits, but probable it could be special-cased somehow, I am sure. -- Cheers, David / dhildenb