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[2003:d8:2f37:2b00:948c:dd9f:29c8:73f4]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45b7e8ab093sm150508665e9.22.2025.09.01.01.05.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Sep 2025 01:05:50 -0700 (PDT) Message-ID: Date: Mon, 1 Sep 2025 10:05:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/7] mm/gup: local lru_add_drain() to avoid lru_add_drain_all() To: Hugh Dickins , Andrew Morton Cc: Will Deacon , Shivank Garg , Matthew Wilcox , Christoph Hellwig , Keir Fraser , Jason Gunthorpe , John Hubbard , Frederick Mayle , Peter Xu , "Aneesh Kumar K.V" , Johannes Weiner , Vlastimil Babka , Alexander Krabler , Ge Yang , Li Zhe , Chris Li , Yu Zhao , Axel Rasmussen , Yuanchu Xie , Wei Xu , Konstantin Khlebnikov , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <165ccfdb-16b5-ac11-0d66-2984293590c8@google.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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <165ccfdb-16b5-ac11-0d66-2984293590c8@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: nS04l-FhbILlTgyJ2yulG_9_C8XGU81EtWhn5SjOF28_1756713952 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: rspam07 X-Rspamd-Queue-Id: F28F5A000E X-Stat-Signature: em53piz91bhymzgqw6pe9jmmxd6qazo4 X-Rspam-User: X-HE-Tag: 1756713954-167724 X-HE-Meta: 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 4lLNS1kq 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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 31.08.25 11:08, Hugh Dickins wrote: > In many cases, if collect_longterm_unpinnable_folios() does need to > drain the LRU cache to release a reference, the cache in question is > on this same CPU, and much more efficiently drained by a preliminary > local lru_add_drain(), than the later cross-CPU lru_add_drain_all(). > > Marked for stable, to counter the increase in lru_add_drain_all()s > from "mm/gup: check ref_count instead of lru before migration". > Note for clean backports: can take 6.16 commit a03db236aebf ("gup: > optimize longterm pin_user_pages() for large folio") first. > > Signed-off-by: Hugh Dickins > Cc: > --- > mm/gup.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/gup.c b/mm/gup.c > index 82aec6443c0a..9f7c87f504a9 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2291,6 +2291,8 @@ static unsigned long collect_longterm_unpinnable_folios( > struct folio *folio; > long i = 0; > > + lru_add_drain(); > + > for (folio = pofs_get_folio(pofs, i); folio; > folio = pofs_next_folio(folio, pofs, &i)) { > Do we really want to drain all the time we enter collect_longterm_unpinnable_folios(), or only if we detect an actual problem? (unexpected reference?) -- Cheers David / dhildenb