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Shutemov" , John Hubbard , David Rientjes , Vlastimil Babka , Hugh Dickins , Kefeng Wang , Barry Song <21cnbao@gmail.com>, Alistair Popple Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20231204102027.57185-1-ryan.roberts@arm.com> <20231204102027.57185-5-ryan.roberts@arm.com> <71040a8c-4ea1-4f21-8ac8-65f7c25c217e@redhat.com> <126c3b71-1acc-4851-9986-4228cb8a8660@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: <126c3b71-1acc-4851-9986-4228cb8a8660@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-Stat-Signature: 6h3wbdgm4rcxt1ubugk3tkq9gjhcaorf X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B2A34A0022 X-HE-Tag: 1701955722-254422 X-HE-Meta: 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 N646mSae MeiqcoTdnc4zNz/Wwb5g9RNwP6E6qtnCZoAXa+c5Iuik0Iegft+f/V4j6rMKdksDHWSf3FDskq+xxQ0FF9uXL+28ChhI6O88kkaDjKBSS9YuYtd5ClNlcU0X3y+08NN31loICLXK1KOMQkTL8sS9/9vXLmXPA55P/Pb1mXczCzp7Y7aAT9jJxFrwXPAfThrt7kQBXg9vd4+33i6Xb1i/D/58ImcwZmve9qteB/2WWXaGpIe5kjs6H39S4hDuMz7R6/sg9biWkhfQ/Q3Iyt/ncknAxIUeLVFij/sKAmsgWxRDmDNahaWYwg5yb2epDQ/iQzKmfJBc/rq1IRo+2mmUJy0X5A01IjBNRdlFcyK0ARmuZA4V+RtHi2CzWwW4MObk+IdqHbyPY9Dk97BH9M4qAjb4CJmerC7RIQTuaEPAFs01skLmzd/aMVbJ5hJwNTRL/oIrseYeyNpGW56nQdZL8dwYFzm5GoXWGCaTiSpk6SkdIeew= 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: >> >> Right, but you know from the first loop which order is applicable (and will be >> fed to the second loop) and could just pte_unmap(pte) + tryalloc. If that fails, >> remap and try with the next orders. > > You mean something like this? > > pte = pte_offset_map(vmf->pmd, vmf->address & PMD_MASK); > if (!pte) > return ERR_PTR(-EAGAIN); > > order = highest_order(orders); > while (orders) { > addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order); > if (!pte_range_none(pte + pte_index(addr), 1 << order)) { > order = next_order(&orders, order); > continue; > } > > pte_unmap(pte); > > folio = vma_alloc_folio(gfp, order, vma, addr, true); > if (folio) { > clear_huge_page(&folio->page, vmf->address, 1 << order); > return folio; > } > > pte = pte_offset_map(vmf->pmd, vmf->address & PMD_MASK); > if (!pte) > return ERR_PTR(-EAGAIN); > > order = next_order(&orders, order); > } > > pte_unmap(pte); > > I don't really like that because if high order folio allocations fail, then you > are calling pte_range_none() again for the next lower order; once that check has > succeeded for an order it shouldn't be required for any lower orders. In this > case you also have lots of pte map/unmap. I see what you mean. > > The original version feels more efficient to me. Yes it is. Adding in some comments might help, like /* * Find the largest order where the aligned range is completely prot_none(). Note * that all remaining orders will be completely prot_none(). */ ... /* Try allocating the largest of the remaining orders. */ > >> >> That would make the code certainly easier to understand. That "orders" magic of >> constructing, filtering, walking is confusing :) >> >> >> I might find some time today to see if there is an easy way to cleanup all what >> I spelled out above. It really is a mess. But likely that cleanup could be >> deferred (but you're touching it, so ... :) ). > > I'm going to ignore the last 5 words. I heard the "that cleanup could be > deferred" part loud and clear though :) :) If we could stop passing orders into thp_vma_allowable_orders(), that would probably be the biggest win. It's just all a confusing mess. -- Cheers, David / dhildenb