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b=eyN+e6X4tm2Lp7KCNpBGiVXo1xBpSrkAzJ4DEe+2iUAPt86j9ZkhDC0cfxFTHhgay no/k/Auzl7iLDhRJZKqv0wn3dOmIl7Ejo+to1t0zhjJ3ONQ4lHECKlAZfVXEAz2mu/ 0bLuuVxW1ot9fyc5u17BSJ2JE0y1ENfGc8RTtzQAY4Ppdt+eREuIQLIvNGmrs2ouYb BLrBzaiTXBddrLxNOhVvHb4TuHmEO8Gz78AFrBvUi4OQ0yj5T8cefv4FyQOobCggGJ eLWHOkTn8BuoFxluLX88uMOI6MhYXVuBE0YzfR+4WcPbMryCmQjzIRmspHlcn8Mf29 XdM2g4d1PTR1w== Message-ID: <63a72a5c-6e24-4513-a83c-d8f63df3a600@kernel.org> Date: Wed, 26 Aug 2026 10:27:12 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v3 0/8] batch lookups in follow_page_mask() To: Christoph Hellwig , Rik van Riel Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, Andrew Morton , Jason Gunthorpe , John Hubbard , Peter Xu , linux-mm@kvack.org References: <20260811025157.1632867-1-riel@surriel.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 624BE100007 X-Stat-Signature: qzt7ojxnffaxziuit4eowekekxjk1t5d X-HE-Tag: 1787732837-552116 X-HE-Meta: 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 bGDUatbA ZlVl+iY3NyqVZ+1ORDIZ9dkQL6mK6u20jPKWO5gN/wvi49M/+RTxjaIDomNG+WGTPdLelEbw8hVChZ2IwllhLvBWbCuYo3d3sLzzoYSiu12x+ZK8+AsnvyTgtpYLnbb4tuP6tah2TO7KQrK9qt/mcs0aTiFCLhMVLXoC7QTg6lxTRxlcqNNlw9uQFO2xlp/a5a2auYqyDUt2CBwR0IaEAsiX40ANtbMpUc+mTSqk8Sbg2V4LLpjkKk+3VbRViMZGfPyOUSDR72gsCKaFsMmd5qhBIsWnyTV9x3nKPrZb9qEG3oNjwO4dv8gh/xA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/26/26 09:35, Christoph Hellwig wrote: > On Tue, Aug 25, 2026 at 09:39:14PM -0700, Christoph Hellwig wrote: >> The other callers of iov_iter_extract_bvecs matter more, but this is >> the main user. >> >> And iov_iter_extract_bvecs right now is very inefficient when used >> on larger folios, as each call to iov_iter_extract_bvecs and thus >> iov_iter_extract_pages and iov_iter_extract_user_pages can only >> fill in up to 256 pages. On x86 that is a single PMD mapped >> folio. Passing down the bio_vec array means that for PMD-mapped >> ranges we reduce the calls into pin_user_pages_fast by a factor >> of 256. > > Also in addition to reducing the calls to pin_user_pages_fast, it also > removes a fair amount of work to recalculate the bio_len in the > get_contig_folio_len loop in iov_iter_extract_bvecs, which has shown up > in profiles (although only marginally so). We could think of a mechanism that fills a given structure in a better way, and I think we recently discussed returning folio ranges, and might to that through something like phyr (or however that is called :) ). But that's really not something is would mix into this work here. -- Cheers, David