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(p200300cbc7088a00362b7e34a3bc9ddf.dip0.t-ipconnect.de. [2003:cb:c708:8a00:362b:7e34:a3bc:9ddf]) by smtp.gmail.com with ESMTPSA id h11-20020a05600c314b00b0041490467febsm2607327wmo.38.2024.03.27.09.29.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Mar 2024 09:29:51 -0700 (PDT) Message-ID: Date: Wed, 27 Mar 2024 17:29:50 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6] mm/migrate: split source folio if it is on deferred split list To: Zi Yan , linux-mm@kvack.org Cc: Andrew Morton , "Matthew Wilcox (Oracle)" , Yang Shi , Huang Ying , "Kirill A . Shutemov" , Ryan Roberts , Baolin Wang , "Yin, Fengwei" , SeongJae Park , linux-kernel@vger.kernel.org References: <20240326150031.569387-1-zi.yan@sent.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: <20240326150031.569387-1-zi.yan@sent.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: rspam06 X-Rspamd-Queue-Id: 8D143C0035 X-Stat-Signature: 3f5x9tnofrtzm9rweex3etxrjc7sf5b9 X-HE-Tag: 1711556997-754116 X-HE-Meta: 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 oAbEcu91 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 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 26.03.24 16:00, Zi Yan wrote: > From: Zi Yan > > If the source folio is on deferred split list, it is likely some subpages > are not used. Split it before migration to avoid migrating unused subpages. > > Commit 616b8371539a6 ("mm: thp: enable thp migration in generic path") > did not check if a THP is on deferred split list before migration, thus, > the destination THP is never put on deferred split list even if the source > THP might be. The opportunity of reclaiming free pages in a partially > mapped THP during deferred list scanning is lost, but no other harmful > consequence is present[1]. > > From v5: > 1. Fixed an error in migrate_misplaced_folio() reported by Baolin Wang[3]. > > From v4: > 1. Simplify _deferred_list check without locking and do not count as > migration failures. (per Matthew Wilcox) > > From v3: > 1. Guarded deferred list code behind CONFIG_TRANSPARENT_HUGEPAGE to avoid > compilation error (per SeongJae Park). > > From v2: > 1. Split the source folio instead of migrating it (per Matthew Wilcox)[2]. > > From v1: > 1. Used dst to get correct deferred split list after migration > (per Ryan Roberts). > > [1]: https://lore.kernel.org/linux-mm/03CE3A00-917C-48CC-8E1C-6A98713C817C@nvidia.com/ > [2]: https://lore.kernel.org/linux-mm/Ze_P6xagdTbcu1Kz@casper.infradead.org/ > [3]: https://lore.kernel.org/linux-mm/df9a644c-a007-46ac-98e3-61d4014fcfff@linux.alibaba.com/ > > Fixes: 616b8371539a ("mm: thp: enable thp migration in generic path") > Signed-off-by: Zi Yan > --- > mm/migrate.c | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 1dbe5bd927de..a31aa75d223d 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1652,6 +1652,29 @@ static int migrate_pages_batch(struct list_head *from, > > cond_resched(); > > + /* > + * The rare folio on the deferred split list should > + * be split now. It should not count as a failure. > + * Only check it without removing it from the list. > + * Since the folio can be on deferred_split_scan() > + * local list and removing it can cause the local list > + * corruption. Folio split process below can handle it > + * with the help of folio_ref_freeze(). > + * > + * nr_pages > 2 is needed to avoid checking order-1 > + * page cache folios. They exist, in contrast to > + * non-existent order-1 anonymous folios, and do not > + * use _deferred_list. > + */ > + if (nr_pages > 2 && > + !list_empty(&folio->_deferred_list)) { > + if (try_split_folio(folio, split_folios) == 0) { > + stats->nr_thp_split += is_thp; > + stats->nr_split++; > + continue; > + } > + } > + > /* > * Large folio migration might be unsupported or > * the allocation might be failed so we should retry Acked-by: David Hildenbrand -- Cheers, David / dhildenb