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[2003:d8:2f2c:5500:988:23f9:faa0:7232]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b47285c9f9sm2039057f8f.93.2025.07.04.02.38.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Jul 2025 02:38:27 -0700 (PDT) Message-ID: Date: Fri, 4 Jul 2025 11:38:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: fault in complete folios instead of individual pages for tmpfs To: Baolin Wang , akpm@linux-foundation.org, hughd@google.com Cc: ziy@nvidia.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <440940e78aeb7430c5cc8b6d2088ae98265b9809.1751599072.git.baolin.wang@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: <440940e78aeb7430c5cc8b6d2088ae98265b9809.1751599072.git.baolin.wang@linux.alibaba.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 9z9g6kr15FtmICTUPvdXamKB9Sj5mMwPmXSa-4CkDN0_1751621909 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: mesdnati1oriq5yhtcm9x9jjoyptitmf X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: CC14E100008 X-HE-Tag: 1751621911-445900 X-HE-Meta: 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 YNbLqLFy 4DXSy+c8HYM/p4lwcahE8SfGxlqQxP+FvqyCH1RFfYdCLfKVjDrAnWcX/5TQAMjATVNqKWKCCapaU0+lJLZb11UfOaDIv+MVr6TGSN9qTB7OA2RwOHcXCM7l7RX33ZXdkFXOwB09xxJENzs279Im6tXiv/NeGSPNa7eJkSZ5QP+6yG9rPkaGcod9vE7kWBr1sJ9+CXkAeWQqIf8nfQV7D74UWND5lzlhU5jJIb1Yu+6zVFsohpU1Pq5inYsAe7DUnb7vihw2dKmF+lPBsBL5fIADTF017h31CTWQee1IfFF7qEX00PQYfLEa5Q/97FZlL8fR6+/Yi5LTmIXJ5GI04LCIy8tFc8orvo1w8UEzROyd9M13LEF2VOffPSsUNkTbaX9pkw9fc278tc+91KUb/bDwcNppttB/eXczb2BiGK/tQMfDblST/DGI2RNTSSAp5p3M9gjHVLz/ox64B26G3kuYWDHx7MGciEyjY 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 04.07.25 05:19, Baolin Wang wrote: > After commit acd7ccb284b8 ("mm: shmem: add large folio support for tmpfs"), > tmpfs can also support large folio allocation (not just PMD-sized large > folios). > > However, when accessing tmpfs via mmap(), although tmpfs supports large folios, > we still establish mappings at the base page granularity, which is unreasonable. > > We can map multiple consecutive pages of a tmpfs folios at once according to > the size of the large folio. On one hand, this can reduce the overhead of page > faults; on the other hand, it can leverage hardware architecture optimizations > to reduce TLB misses, such as contiguous PTEs on the ARM architecture. > > Moreover, tmpfs mount will use the 'huge=' option to control large folio > allocation explicitly. So it can be understood that the process's RSS statistics > might increase, and I think this will not cause any obvious effects for users. > > Performance test: > I created a 1G tmpfs file, populated with 64K large folios, and write-accessed it > sequentially via mmap(). I observed a significant performance improvement: > > Before the patch: > real 0m0.158s > user 0m0.008s > sys 0m0.150s > > After the patch: > real 0m0.021s > user 0m0.004s > sys 0m0.017s > > Signed-off-by: Baolin Wang > --- > Changes from v1: > - Drop the unnecessary IS_ALIGNED() check, per David. > - Update the commit message, per David. > --- > mm/memory.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 0f9b32a20e5b..9944380e947d 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5383,10 +5383,10 @@ vm_fault_t finish_fault(struct vm_fault *vmf) > > /* > * Using per-page fault to maintain the uffd semantics, and same > - * approach also applies to non-anonymous-shmem faults to avoid > + * approach also applies to non shmem/tmpfs faults to avoid > * inflating the RSS of the process. > */ > - if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma)) || > + if (!vma_is_shmem(vma) || unlikely(userfaultfd_armed(vma)) || > unlikely(needs_fallback)) { > nr_pages = 1; > } else if (nr_pages > 1) { Acked-by: David Hildenbrand -- Cheers, David / dhildenb