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[2003:cb:c736:ca00:b4c3:24bd:c2f5:863c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38c2a189283sm10379549f8f.59.2025.01.26.23.46.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 26 Jan 2025 23:46:18 -0800 (PST) Message-ID: Date: Mon, 27 Jan 2025 08:46:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: page_ref tracepoints To: Matthew Wilcox , linux-mm@kvack.org Cc: Joonsoo Kim , linux-fsdevel@vger.kernel.org References: 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: nOPo-22SG65dLu8U1uy2Y7MHMXZrBOdk4gCt0UToowk_1737963980 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: DF7E414000D X-Stat-Signature: oy4xpob4wb3eixrnmjjwd3mneuy3xs15 X-Rspamd-Server: rspam08 X-Rspam-User: X-HE-Tag: 1737963983-629981 X-HE-Meta: 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 y/e1Hci5 fQaIyE4ODlj3cOVFQs20fXS9LRuAApheojxOhmLjCzA4Zc1/ZRXyxEh62TU8bRxidJv4Mg54VXdghWBgg1ZODkZCjSg5whVuWeUv2+mOr1G662t6KT7fVFA64aXYNaR2Qo0hF+36rYrP3dZ1fCgSD+2NtBsj9mvtOFfScuF16H6j4uZo5zxv09N42I2McjIgLHtl+fMO9+5zdMiQBIW2lpQOQ7M36TCsaQhw82xrBzBxfgiYMwO+wqUBfmCR0EkstPi+W7uDuAXqgn9C6tetBCcLu1Xfcrt3V8vTTOK0LQ1tsH28uChe69d7i1hGrgyZIRkr9EVqBc8044yiJw942ASsOAASydg3rBakmLBBr4Vm5cOKfJKD34ljx7PM1BCfRW1EtErDsOnMgHmVGsZH2YdCIsx5MQOFzA2Ky6Du2GnZ4toyTmIbs9S2yZ2VpJC8F7K7y 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 23.01.25 20:55, Matthew Wilcox wrote: > The page reference count tracepoints currently look like this: > > __entry->pfn = page_to_pfn(page); > __entry->flags = page->flags; > __entry->count = page_ref_count(page); > __entry->mapcount = atomic_read(&page->_mapcount); > __entry->mapping = page->mapping; > __entry->mt = get_pageblock_migratetype(page); > TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d", > > > Soon, pages will not have a ->mapping, nor a ->mapcount [1]. But they will > still have a refcount, at least for now. put_page() will move out of > line and look something like this: > > void put_page(struct page *page) > { > unsigned long memdesc = page->memdesc; > if (memdesc_is_folio(memdesc)) > return folio_put(memdesc_folio(memdesc)); > BUG_ON(memdesc_is_slab(memdesc)); > ... handle other memdesc types here ... > if (memdesc_is_compound_head(memdesc)) > page = memdesc_head_page(memdesc); > > if (put_page_testzero(page)) > __put_page(page); > } > > What I'm thinking is: > > - Define a set of folio_ref_* tracepoints which dump exactly the same info > as page_ref does today > - Remove mapping & mapcount from page_ref_* functions. Yes, I did not completely remove the mapcount in 6eca32567455db2db38b1126e0d6ad8f0e5c3ed9, but likely I just should have. We're dumping raw values of flags/mappings/mapcount right now, and probably we should drop them all here. I also once thought about introducing folio variants on my todo list to dump actual per-folio fields instead of raw values. One "problematic" part in the current usage are things like page_ref_sub_and_test(), where we end up calling __page_ref_mod_and_test() on something with a refcount of 0 (or could even have been reallocated? not sure) -- Cheers, David / dhildenb