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[2003:cb:c71b:d000:1d1f:238e:aeaf:dbf7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-434d43a100csm80243435e9.1.2024.12.06.02.13.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 06 Dec 2024 02:13:17 -0800 (PST) Message-ID: <315752c5-6129-4c8b-bf8c-0cc26f0ad5c5@redhat.com> Date: Fri, 6 Dec 2024 11:13:16 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v2 00/21] riscv: Introduce 64K base page To: Zi Yan , Xu Lu Cc: paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, ardb@kernel.org, anup@brainfault.org, atishp@atishpatra.org, xieyongji@bytedance.com, lihangjing@bytedance.com, punit.agrawal@bytedance.com, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Linux MM References: <20241205103729.14798-1-luxu.kernel@bytedance.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: kPs40ub0OhR6ok9RrjIyGAUZpq1u5SZ812MEk37pPao_1733479999 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: qxmck8n4et3hkdhknu6d9trx16imprix X-Rspamd-Queue-Id: DB15A20014 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1733479994-500001 X-HE-Meta: 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 gtshgIA2 gq/YUtWI2ZeFFovYvCOdosI/LOYMc+3ttHkdP6DjcYS7uwrY2W6RaiZhcVVWfkVmfcTYjFk/tkFb8bT387hvrzKdHkZzRs3JOa1B1eT3DYiK41hmAXrfS9BtR8JQPU1Fgk3lgxg4U2SV8Z4vT0cwHjhg1kwKcF6WEk45uA8/EBmYZKMqpVV7k7Nwly4imjfQo2L2zUsY+pnQqx+bPgEwUzCTp04UEOZcJy51qgLUVdAUsivVMJKwn2ippwYf2TMQn4Aj+vHg0Y11dx3Ma7571QCw1OS5NT7V1xb1biJmAdygILmlsXLbr1z0MBwGifQd1uq+n0SPcgSq6Y7ynHmfrrkxfI3Q2zb+UI9zBS0uiCQtXy5tdiRhzXI/jmkoyraB1TRkBCJjS7KkNnXzCp20FDerqyV+6eXJgsbrw4ftLYEf8Gm3D5Z2bkcz4g8dEGltlFOZI4rLBdyoP99OGv5P1NNLYd/M30ai+blmias5//A3AuahOTC9By5hBDSOOXTO977DmfQg6g4UoRf8W6C+z4LpgV982nV+BGNHn 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 06.12.24 03:00, Zi Yan wrote: > On 5 Dec 2024, at 5:37, Xu Lu wrote: > >> This patch series attempts to break through the limitation of MMU and >> supports larger base page on RISC-V, which only supports 4K page size >> now. The key idea is to always manage and allocate memory at a >> granularity of 64K and use SVNAPOT to accelerate address translation. >> This is the second version and the detailed introduction can be found >> in [1]. >> >> Changes from v1: >> - Rebase on v6.12. >> >> - Adjust the page table entry shift to reduce page table memory usage. >> For example, in SV39, the traditional va behaves as: >> >> ---------------------------------------------- >> | pgd index | pmd index | pte index | offset | >> ---------------------------------------------- >> | 38 30 | 29 21 | 20 12 | 11 0 | >> ---------------------------------------------- >> >> When we choose 64K as basic software page, va now behaves as: >> >> ---------------------------------------------- >> | pgd index | pmd index | pte index | offset | >> ---------------------------------------------- >> | 38 34 | 33 25 | 24 16 | 15 0 | >> ---------------------------------------------- >> >> - Fix some bugs in v1. >> >> Thanks in advance for comments. >> >> [1] https://lwn.net/Articles/952722/ > > This looks very interesting. Can you cc me and linux-mm@kvack.org > in the future? Thanks. > > Have you thought about doing it for ARM64 4KB as well? ARM64’s contig PTE > should have similar effect of RISC-V’s SVNAPOT, right? What is the real benefit over 4k + large folios/mTHP? 64K comes with the problem of internal fragmentation: for example, a page table that only occupies 4k of memory suddenly consumes 64K; quite a downside. -- Cheers, David / dhildenb