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[2003:cb:c722:3900:648:abee:feaa:96fd]) by smtp.gmail.com with ESMTPSA id u10-20020a5d6daa000000b0033d170a5d6dsm10726222wrs.98.2024.02.19.07.31.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Feb 2024 07:31:15 -0800 (PST) Message-ID: <2c214438-c5df-4831-92e0-57e8b96d6a6f@redhat.com> Date: Mon, 19 Feb 2024 16:31:14 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 01/18] mm: Make folios_put() the basis of release_pages() To: Matthew Wilcox Cc: Andrew Morton , linux-mm@kvack.org References: <20240217022546.1496101-1-willy@infradead.org> <20240217022546.1496101-2-willy@infradead.org> <15797535-3107-4724-acec-7c006da490f3@redhat.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: 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: rspam12 X-Rspamd-Queue-Id: 6CD69140019 X-Stat-Signature: 4aqywxhbk14kfa1cdb83e1cg4hwc3i5d X-HE-Tag: 1708356682-522569 X-HE-Meta: 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 BS7SNu4/ 6ebb22tT9arp/fTTeOQt+1LGL2uigInR8k/N/1gIVoFmqwfdzARWNKJVYQ6JpYvygLb0HrsLOd9UnUXwYYv1OLkgcmEB+0sSZYog1+NIpX4ioKlSGGjWK4341FXvt5nyo4j35igOdpaFCGL+P5U1kJDC+02txQycx2N/UpqFPVfbC8UGW22PZ9lQUsReS3WLqile3+HHNY1xPqp/yyteYgFDMhgLO8fHeMOY1hl4JgnMYxoYoRo/shC23ZWYnngMZWqZsUXIUOg9LNbANMvcaBqa4LTNDKa4wbd8Zk2k31sa2TTnLHzPcb7FwENUnB2hEdxeeHsz7aD0U8jlZDPZdBOCCsMBJI7DPFoXlqFothu4d9OjrxnNAAOOyWULSIlGUUQIlW7IwHHuOpp/7+rlwAEfD+ZF0Z3nEfwOqB0OchkGJt62f972G7N3Gs8xTKGoyehKcDrbBRR8VJaKyw1L8Ixc72Q== 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 19.02.24 16:03, Matthew Wilcox wrote: > On Mon, Feb 19, 2024 at 10:43:06AM +0100, David Hildenbrand wrote: >> On 17.02.24 03:25, Matthew Wilcox (Oracle) wrote: >>> By making release_pages() call folios_put(), we can get rid of the calls >>> to compound_head() for the callers that already know they have folios. >>> We can also get rid of the lock_batch tracking as we know the size >>> of the batch is limited by folio_batch. This does reduce the maximum >>> number of pages for which the lruvec lock is held, from SWAP_CLUSTER_MAX >>> (32) to PAGEVEC_SIZE (15). I do not expect this to make a significant >>> difference, but if it does, we can increase PAGEVEC_SIZE to 31. >>> >> >> I'm afraid that won't apply to current mm-unstable anymore, where we can now >> put multiple references to a single folio (as part of unmapping >> large PTE-mapped folios). > > Argh. I'm not a huge fan of that approach, but let's live with it for > now. I'm hoping we at least can get rid of page ranges at some point (and just have folio + nr_refs), but for the time being there is no way around that due to delayed rmap handling that needs the exact pages (ugh). folios_put_refs() does sound reasonable in any case, although likely "putting multiple references" is limited to zap/munmap/... code paths. > How about this as a replacement patch? It compiles ... > Nothing jumped at me, one comment: [...] > +EXPORT_SYMBOL(folios_put); > + > +/** > + * release_pages - batched put_page() > + * @arg: array of pages to release > + * @nr: number of pages > + * > + * Decrement the reference count on all the pages in @arg. If it > + * fell to zero, remove the page from the LRU and free it. > + * > + * Note that the argument can be an array of pages, encoded pages, > + * or folio pointers. We ignore any encoded bits, and turn any of > + * them into just a folio that gets free'd. > + */ > +void release_pages(release_pages_arg arg, int nr) > +{ > + struct folio_batch fbatch; > + int refs[PAGEVEC_SIZE]; > + struct encoded_page **encoded = arg.encoded_pages; > + int i; > + > + folio_batch_init(&fbatch); > + for (i = 0; i < nr; i++) { > + /* Turn any of the argument types into a folio */ > + struct folio *folio = page_folio(encoded_page_ptr(encoded[i])); > + > + /* Is our next entry actually "nr_pages" -> "nr_refs" ? */ > + refs[fbatch.nr] = 1; > + if (unlikely(encoded_page_flags(encoded[i]) & > + ENCODED_PAGE_BIT_NR_PAGES_NEXT)) > + refs[fbatch.nr] = encoded_nr_pages(encoded[++i]); > + > + if (folio_batch_add(&fbatch, folio) > 0) > + continue; > + folios_put_refs(&fbatch, refs); > + } > + > + if (fbatch.nr) > + folios_put_refs(&fbatch, refs); I wonder if it makes sense to remember if any ref !=1, and simply call folios_put() if that's the case. But I guess the whole point about PAGEVEC_SIZE is that it is very cache-friendly and traversing it a second time (e.g., when all we are doing is freeing order-0 folios) is not too expensive. -- Cheers, David / dhildenb