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[2003:d8:2f1a:f500:4346:f17c:2bde:808c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454cd3d7cf4sm25167465e9.28.2025.07.08.07.53.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Jul 2025 07:53:38 -0700 (PDT) Message-ID: Date: Tue, 8 Jul 2025 16:53:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 08/11] mm/thp: add split during migration support To: Zi Yan Cc: Balbir Singh , linux-mm@kvack.org, akpm@linux-foundation.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, Karol Herbst , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Shuah Khan , Barry Song , Baolin Wang , Ryan Roberts , Matthew Wilcox , Peter Xu , Kefeng Wang , Jane Chu , Alistair Popple , Donet Tom References: <20250306044239.3874247-1-balbirs@nvidia.com> <20250306044239.3874247-9-balbirs@nvidia.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: AcYmtUISM0JyUkt5kZwcjZtldlfEBwEF_UrmdSW-VIM_1751986419 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 5BE538000C X-Stat-Signature: rh7ubdxucm1neep7b93xzbued651og6j X-Rspam-User: X-HE-Tag: 1751986422-924606 X-HE-Meta: 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 nalwxzPt ghmaNZNK6mOuCh8T961NSAh3+hVVFLwuEHM1PZd8rH5znGpbM3Iiz1tt8iPFHJpWz8wrwGRgXhIM5GezwnpXCJxfCM4UpAD70/De2mW9SOyuR5JmS65570UxJ2xHe43ohnLcNYiI/Zv2vQuFtfFFLPtNCvnvah9H2f/FmWBgPlX5JppX9aw/sLyLrUg2Htia7E2w77HeQqKnZyqWRTMuvADQvLDdOilxShm/xtVpU+dac/EmnG4c5r7yAG+ttDkiD77QQ/lIizaNur5uLcZyDEqjPQ725lL3c1uJkNZ9ITL5onsPoitv4mDL73B4MmDYWsilUFsxoyyiYT6EmkPWDViyFqY+eI/hXU4pe0IYbAIVcLxLbW4Bym9gkL/C92IxrRmB+zQ4jDsK51MM9GvZ6Sa/iiFHCnGzNa80J1pTyooGgs9gTnCyawWpCI1STqDowITIOsqpuFJvNnj11UopaLtCTotNASyC4M+pbVhDd2ptFWZvRt4iQJ7zoPtscltjwjxEr 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 08.07.25 16:46, Zi Yan wrote: > On 8 Jul 2025, at 10:38, David Hildenbrand wrote: > >> On 06.03.25 05:42, Balbir Singh wrote: >>> Support splitting pages during THP zone device migration as needed. >>> The common case that arises is that after setup, during migrate >>> the destination might not be able to allocate MIGRATE_PFN_COMPOUND >>> pages. >>> >>> Add a new routine migrate_vma_split_pages() to support the splitting >>> of already isolated pages. The pages being migrated are already unmapped >>> and marked for migration during setup (via unmap). folio_split() and >>> __split_unmapped_folio() take additional isolated arguments, to avoid >>> unmapping and remaping these pages and unlocking/putting the folio. >>> >>> Since unmap/remap is avoided in these code paths, an extra reference >>> count is added to the split folio pages, which will be dropped in >>> the finalize phase. >>> >>> Signed-off-by: Balbir Singh >>> --- >> >> [...] >> >>> remap_page(origin_folio, 1 << order, >>> folio_test_anon(origin_folio) ? >>> RMP_USE_SHARED_ZEROPAGE : 0); >>> @@ -3808,6 +3823,7 @@ bool uniform_split_supported(struct folio *folio, unsigned int new_order, >>> * @lock_at: a page within @folio to be left locked to caller >>> * @list: after-split folios will be put on it if non NULL >>> * @uniform_split: perform uniform split or not (non-uniform split) >>> + * @isolated: The pages are already unmapped >> >> Isolated -> unmapped? Huh? >> >> Can we just detect that state from the folio so we don't have to pass random boolean variables around? >> >> For example, folio_mapped() can tell you if the folio is currently mapped. > > My proposal is to clean up __split_unmapped_folio() to not include > remap(), folio_ref_unfreeze(), lru_add_split_folio(), so that Balbir > can use __split_unmapped_folio() directly. Since the folio is > unmapped and all page table entries are migration entries, __folio_split() > code could be avoided. > > My clean up patch is at: https://lore.kernel.org/linux-mm/660F3BCC-0360-458F-BFF5-92C797E165CC@nvidia.com/. I will make some polish and send it out properly. Works for me as well. -- Cheers, David / dhildenb