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[2003:cb:c70d:8400:ed9b:a3a:88e5:c6a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43f20625592sm14523295e9.10.2025.04.09.02.53.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Apr 2025 02:53:14 -0700 (PDT) Message-ID: Date: Wed, 9 Apr 2025 11:53:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: huge_memory: add folio_mark_accessed() when zapping file THP To: Baolin Wang , akpm@linux-foundation.org Cc: willy@infradead.org, hannes@cmpxchg.org, 21cnbao@gmail.com, ryan.roberts@arm.com, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <39176ab9-33d5-4919-b368-2fd2467f08fe@redhat.com> <0e294c56-d924-4d40-aa24-584235e8c923@linux.alibaba.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: <0e294c56-d924-4d40-aa24-584235e8c923@linux.alibaba.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: I-5EPQuCva770NjdiUYdqXjDRGENHhysulq9r82oEfI_1744192396 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: E628F20009 X-Stat-Signature: ghy48oe7o73oi5bhz19f45amjiazs8wd X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1744192398-516785 X-HE-Meta: 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 PjnbkkhK 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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 09.04.25 11:49, Baolin Wang wrote: > > > On 2025/4/9 17:46, David Hildenbrand wrote: >> On 09.04.25 11:38, Baolin Wang wrote: >>> When investigating performance issues during file folio unmap, I >>> noticed some >>> behavioral differences in handling non-PMD-sized folios and PMD-sized >>> folios. >>> For non-PMD-sized file folios, it will call folio_mark_accessed() to >>> mark the >>> folio as having seen activity, but this is not done for PMD-sized folios. >>> >>> This might not cause obvious issues, but a potential problem could be >>> that, >>> it might lead to reclaim hot file folios under memory pressure, as quoted >>> from Johannes: >>> >>> " >>> Sometimes file contents are only accessed through relatively short-lived >>> mappings. But they can nevertheless be accessed a lot and be hot. It's >>> important to not lose that information on unmap, and end up kicking out a >>> frequently used cache page. >>> " >>> >>> Therefore, we should also add folio_mark_accessed() for PMD-sized file >>> folios when unmapping. >>> >>> Signed-off-by: Baolin Wang >>> Acked-by: Johannes Weiner >>> Acked-by: Zi Yan >>> --- >>> Changes from RFC: >>>   - Update the commit message, per Johannes. >>>   - Collect Acked tags from Johannes and Zi. Thanks. >>> --- >>>   mm/huge_memory.c | 4 ++++ >>>   1 file changed, 4 insertions(+) >>> >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index 2a47682d1ab7..955781b4e946 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -2260,6 +2260,10 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct >>> vm_area_struct *vma, >>>                   zap_deposited_table(tlb->mm, pmd); >>>               add_mm_counter(tlb->mm, mm_counter_file(folio), >>>                          -HPAGE_PMD_NR); >>> + >>> +            if (flush_needed && pmd_young(orig_pmd) && >>> +                likely(vma_has_recency(vma))) >>> +                folio_mark_accessed(folio); >> >> So the flush_needed check is really just a pmd_present() check. (the >> latter would be clearer, but I don't mind) > > Yes, we've already checked pmd_present() before, so I assume the > flush_needed check is cheaper:) Maybe :) -- Cheers, David / dhildenb