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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4361e54ef20sm19907675e9.5.2024.12.11.07.03.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Dec 2024 07:03:04 -0800 (PST) Message-ID: Date: Wed, 11 Dec 2024 16:03:02 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 4/6] mm: Introduce a pageflag for partially mapped folios To: Usama Arif , akpm@linux-foundation.org, linux-mm@kvack.org Cc: hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, roman.gushchin@linux.dev, yuzhao@google.com, npache@redhat.com, baohua@kernel.org, ryan.roberts@arm.com, rppt@kernel.org, willy@infradead.org, cerasuolodomenico@gmail.com, ryncsn@gmail.com, corbet@lwn.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@meta.com References: <20240830100438.3623486-1-usamaarif642@gmail.com> <20240830100438.3623486-5-usamaarif642@gmail.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: <20240830100438.3623486-5-usamaarif642@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 9gHYW0WdqW2zrgVH5EXuNuPF7ZS6QCmz_RXU3kV2Ib0_1733929401 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: rspam10 X-Rspamd-Queue-Id: 060A72001C X-Stat-Signature: x3qsam7ih1rgdzrtf7q5k66eqfyenckf X-Rspam-User: X-HE-Tag: 1733929381-532178 X-HE-Meta: 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 6OBvWGn1 OWXs9vCGHCed/LqUXhMthUyCB+qHUsLj7GpjCF4kulAoimNTCz4LkWiAOj2EpVzItrfqJ12zZf6AnaTXg9VASOOCq47KE81iHAZK4BGni8bQNqeHfPVHX4nOdT813hdGQ9S5Lom8iJxW+fMv4WbNLrePTBxhUTAjKlJQ4zaLxa71gnsUVYy12Ud87BtJvPwPzsKxqvbZu3m7Rz+c+lpRsUn+yzTl4XZgBGwmuj8Dd3PhgRzzeiPRhQyGa2OyqVOTqowyk4TfqcXwrp17uwRTOXjGidqtuYRx+OP+pYlbBBW1D5zAXE7mR+m8i/ebi0YW/exNpo4hgTKf7zoiM7nsnF6vkaw1dItxZEYr+Rdoxk2ZhUiETkeOEDBO4pBO+5nRMIR9XG0rj8u3SDeGzkTS98MZb96+unUs8uWj3iEpLMpYyBFokU+I1AZqlb9wRmplwRha1 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 30.08.24 12:03, Usama Arif wrote: > Currently folio->_deferred_list is used to keep track of > partially_mapped folios that are going to be split under memory > pressure. In the next patch, all THPs that are faulted in and collapsed > by khugepaged are also going to be tracked using _deferred_list. > > This patch introduces a pageflag to be able to distinguish between > partially mapped folios and others in the deferred_list at split time in > deferred_split_scan. Its needed as __folio_remove_rmap decrements > _mapcount, _large_mapcount and _entire_mapcount, hence it won't be > possible to distinguish between partially mapped folios and others in > deferred_split_scan. > > Eventhough it introduces an extra flag to track if the folio is > partially mapped, there is no functional change intended with this > patch and the flag is not useful in this patch itself, it will > become useful in the next patch when _deferred_list has non partially > mapped folios. > > Signed-off-by: Usama Arif > --- > include/linux/huge_mm.h | 4 ++-- > include/linux/page-flags.h | 13 +++++++++++- > mm/huge_memory.c | 41 ++++++++++++++++++++++++++++---------- > mm/memcontrol.c | 3 ++- > mm/migrate.c | 3 ++- > mm/page_alloc.c | 5 +++-- > mm/rmap.c | 5 +++-- > mm/vmscan.c | 3 ++- > 8 files changed, 56 insertions(+), 21 deletions(-) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 4da102b74a8c..0b0539f4ee1a 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -333,7 +333,7 @@ static inline int split_huge_page(struct page *page) > { > return split_huge_page_to_list_to_order(page, NULL, 0); > } > -void deferred_split_folio(struct folio *folio); > +void deferred_split_folio(struct folio *folio, bool partially_mapped); > > void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > unsigned long address, bool freeze, struct folio *folio); > @@ -502,7 +502,7 @@ static inline int split_huge_page(struct page *page) > { > return 0; > } > -static inline void deferred_split_folio(struct folio *folio) {} > +static inline void deferred_split_folio(struct folio *folio, bool partially_mapped) {} > #define split_huge_pmd(__vma, __pmd, __address) \ > do { } while (0) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 2175ebceb41c..1b3a76710487 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -186,6 +186,7 @@ enum pageflags { > /* At least one page in this folio has the hwpoison flag set */ > PG_has_hwpoisoned = PG_active, > PG_large_rmappable = PG_workingset, /* anon or file-backed */ > + PG_partially_mapped = PG_reclaim, /* was identified to be partially mapped */ > }; > > #define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1) > @@ -859,8 +860,18 @@ static inline void ClearPageCompound(struct page *page) > ClearPageHead(page); > } > FOLIO_FLAG(large_rmappable, FOLIO_SECOND_PAGE) > +FOLIO_TEST_FLAG(partially_mapped, FOLIO_SECOND_PAGE) > +/* > + * PG_partially_mapped is protected by deferred_split split_queue_lock, > + * so its safe to use non-atomic set/clear. Just stumbled over that. In my understanding, this assumption is wrong. I don't think anything prevents other PF_ANY (PG_anon_exclusive, PG_PG_hwpoison) / PF_SECOND (PF_has_hwpoisoned) flags from getting modified concurrently I'm afraid. -- Cheers, David / dhildenb