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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-387824c384esm1552871f8f.56.2024.12.11.07.50.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Dec 2024 07:50:13 -0800 (PST) Message-ID: <42869071-64a9-47d1-867d-9ddede6bf430@redhat.com> Date: Wed, 11 Dec 2024 16:50:12 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: The future of PageAnonExclusive To: Matthew Wilcox Cc: Ryan Roberts , "linux-mm@kvack.org" References: <9c2a17af-4df8-42f0-93c8-83133b6104fd@redhat.com> <3a9e7c3b-7b69-4f16-80ea-b1a0d4dba853@redhat.com> <41e5c2c6-01bb-40ab-a7bf-5b4e827377f8@arm.com> <9378073b-06bb-47b4-8435-32aba67d5845@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: Q85H8-MMgWD_qJHgxAG_9_zddZojptwJNdWN6hgQ5js_1733932214 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: F29D614000C X-Stat-Signature: mjr43tpnwja3dpt3ywwhoika3uw45ncz X-Rspam-User: X-HE-Tag: 1733932201-765263 X-HE-Meta: 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 OvGyGW39 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.035544, 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 11.12.24 16:45, Matthew Wilcox wrote: > On Wed, Dec 11, 2024 at 03:49:12PM +0100, David Hildenbrand wrote: >> On 11.12.24 15:25, Ryan Roberts wrote: >>> On 11/12/2024 11:56, David Hildenbrand wrote: >>>> Now CCing the correct Willy :) >>>> >>>> On 11.12.24 12:55, David Hildenbrand wrote: >>>>> Hi, >>>>> >>>>> PageAnonExclusive (PAE) is working very reliable at this point. But >>>>> especially in the context of THPs (large folios) we'd like to do better: >>>>> >>>>> (1) For PTE-mapped THP, we have to maintain it per page. We'd like to >>>>>       avoid per-page flags as good as possible (e.g., waste in "struct >>>>>       page",  touching many cachelines). >>> >>> Presumably also important for the Glorious Future where struct page is just a >>> pointer and struct folio (et al) is allocated dynamically? >> >> I think Willy mentioned that there might be ways to encode it in the 8-byte >> for the "tail" pages. > > Yes. For anon memory, the page->memdesc has a 4-bit 'type' and the > remaining 60 bits is a pointer to a struct folio (allocated from a slab > with 16 byte alignment). The current list of types [1] has file folios > as type 2 and anon folios as type 3. We could allocate a type to be > 'anon exclusive', thus essentially giving us an anon-exclusive bit. Right. > > [1] https://kernelnewbies.org/MatthewWilcox/Memdescs > > Don't get too excited about "we're almost out of types". The "managed" > type has subtypes. We could also collapse "file" and "anon" into a > single type and distinguish between them with a bit in the folio. > > Anyway, yes, we can do one per-page flag. Two per-page flags starts to > get dicey. hwpoison? :/ -- Cheers, David / dhildenb