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(p200300cbc72237006501892506f9fcdc.dip0.t-ipconnect.de. [2003:cb:c722:3700:6501:8925:6f9:fcdc]) by smtp.gmail.com with ESMTPSA id q3-20020adff783000000b003332febec90sm9626011wrp.7.2023.12.04.04.28.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 Dec 2023 04:29:00 -0800 (PST) Message-ID: <890f4455-bf1b-437b-a355-7895e4dd3085@redhat.com> Date: Mon, 4 Dec 2023 13:28:59 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 4/4] mm/mmu_gather: Store and process pages in contig ranges To: Ryan Roberts , Zi Yan , Matthew Wilcox Cc: Will Deacon , "Aneesh Kumar K.V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Christian Borntraeger , Sven Schnelle , Arnd Bergmann , Yu Zhao , "Kirill A. Shutemov" , Yin Fengwei , Yang Shi , "Huang, Ying" , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230810103332.3062143-1-ryan.roberts@arm.com> <20230810103332.3062143-5-ryan.roberts@arm.com> <800937DA-BAD0-4C60-B155-AECCA21E955E@nvidia.com> <1a0f5cb8-421c-4f28-a986-f3c381406e81@arm.com> <90EC4C0D-0254-4B93-AFD5-3C09580A77DE@nvidia.com> <6dd6164a-1dd5-46e7-bcf7-b62ff5c6e8ec@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: <6dd6164a-1dd5-46e7-bcf7-b62ff5c6e8ec@arm.com> X-Mimecast-Spam-Score: 0 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: rspam12 X-Rspamd-Queue-Id: BA70340025 X-Stat-Signature: eh9wh4s1gx4ifonwogt93yunag8n1jfx X-HE-Tag: 1701692944-792980 X-HE-Meta: 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 V7K1AZDq k1ppQPFkKby3Bj/+HpENW7oDougV0FGurHWjvdh8ewn2DTKHsItNrzmUEJ+z11PPy5SeqQTW3EHyF1+MKeUMNdJ/QdnwORijZuJvCv/BMfZf27ZEuGmL1tv8INz3Sa32YXg2Ortd0U8b53GIOvjdN37bttmUPyH46ug16Fs8d8pVHuZc7h9enMUt8y3IDNj1MiBbQC7E1vwHS3uVkOogTOOjdV9sMs84pBJjSI51sSotXYYp5OGcT9vrQYsWXauwOiC7WnjQPEwY5A8cP7n2NZm+us+xNkODF5DJ9XuowLENfJpxEnsr4D7k/Z5VlMRnQDrNuso0qdDzXzRkEkEH/qjtA2GqxmpzjBHO89c9jchTYZlq1MqFe9DMPIa0Qw+kJWx1XPUsCX8ek6QLDNrIyUyZ5AO1C72oyMzPoI0Lqpmz+Y9D14WS8MrRnSfXbAH2lB0KNqmUrx2ZGJpvLhA514ku7zQ== 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 04.12.23 13:26, Ryan Roberts wrote: >>>> >>>> Also, struct page (memmap) might not be always contiguous, using struct page >>>> points to represent folio range might not give the result you want. >>>> See nth_page() and folio_page_idx() in include/linux/mm.h. >>> >>> Is that true for pages within the same folio too? Or are all pages in a folio >>> guarranteed contiguous? Perhaps I'm better off using pfn? >> >> folio_page_idx() says not all pages in a folio is guaranteed to be contiguous. >> PFN might be a better choice. > > Hi Zi, Matthew, > > Zi made this comment a couple of months back that it is incorrect to assume that > `struct page`s within a folio are (virtually) contiguous. I'm not sure if that's > really the case though? I see other sites in the source that do page++ when > iterating over a folio. e.g. smaps_account(), splice_folio_into_pipe(), > __collapse_huge_page_copy(), etc. > > Any chance someone could explain the rules? With the vmemmap, they are contiguous. Without a vmemmap, but with sparsemem, we might end up allocating one memmap chunk per memory section (e.g., 128 MiB). So, for example, a 1 GiB hugetlb page could cross multiple 128 MiB sections, and therefore, the memmap might not be virtually consecutive. -- Cheers, David / dhildenb