From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793694529; b=dyEqsvNRVqcPBQ71JMxiSzKn0xTfIp1zePFRNBbIX3esFolxU1nfeqaD817AaLpkq44l bMp3j7gdCFNZbRwLiTN3KXZyLlncl9p613Rb1TV0iP8o4t2k9+CLDa6eUibNQwrXxkjz4 y/gC4SJ8uyuw6UQqBOlsMwWsHCd+OI6wu1bZgThlyM+g1YlgZ0b+9viTldqo3jfBx7+eH fxIWU4F7gOY5kq4wyWYbBFEfgzRboaM4Rv4Uyq4EMqR+vcXtNAJ+0Au7uuG2BAmTjeqR8 qyNuLXL1bWwSqP7KKmYD6XTOloblzeGLCLuCv21E+58uSIKGgorLyOut7aXiMMkznyQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793694529; h=Received:DKIM-Signature:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:Content-Language:Autocrypt:In-Reply-To: Content-Type:Content-Transfer-Encoding; bh=JaOz5oG8lXkw1B13R5Aj/6B+VG1aflC2P3pGdWg2ao8=; b=tpvKz5tW9LiWrApNEsuNNqi+whn6b21SCMwcSxW3k3c9VyxozEmBVxfZwm+Mam/+fSjq lZDl7tGHYBC2qtvZRlLnRV1dXmibLASEUyYBTMN8SrM2TDLG66ZD25+9s4gCXM6By0PJC d7pMrneVaeRrqeI6nADFt0fCBYI/9Z01PdD+3hqy99szIW+Q4qQRDrfWALRNphOj5rgAv VTvjuGbs1e0/GD/4pzfbWiF7nkhgx32QfcfHe448JQ4VdeKGcPHu29YsdElwJibFipnWh zHJ0RwHIc034IDi51UgRtfq2cVWhidQ0VzpewvoVFtn3qFkh1Usl/urFOr/xQhizCjA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=lt4QPuwU; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C3E91606A326; Tue, 3 Nov 2026 08:28:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=lt4QPuwU Received: by smtp.kernel.org (Postfix) with ESMTPSA id 903F81F000C1; Tue, 3 Nov 2026 08:28:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793694528; bh=JaOz5oG8lXkw1B13R5Aj/6B+VG1aflC2P3pGdWg2ao8=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=lt4QPuwUBBDihgRfS3d6ycNZp+q7tmtYJcB/AHlkqiEQOgcVoFinBwynsp4bCFJzK 31xkL+CCfnK7Vyq7HSeyvcKibwmQYPDt1R/Q9Aty48njdYhF7hVd02W1u8DqwyP032 Yy4ok3dHsGvdbXlxIlsKzeqcHQROHSEa8cylgZJ+J4gm4Spki0Q0dwgAwmlgq7IqRA ARSTMNXPLQ0ROEgzmKOSU7Mfnb9zzobP6+vAC/5AO9itGe3iYSauIC09VNJGdl96PT YDl6d/ghh3WdD4IcXdJCrk2QOmKylbuhlUI3xfboG5bvCdANTxl/C/NyfPJd1KBneb sbDwU/dj+SEZQ== Message-ID: Date: Tue, 3 Nov 2026 09:28:40 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/shmem: remove truncated folios from the page cache in batches To: Qiliang Yuan , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Hugh Dickins , Baolin Wang , "Matthew Wilcox (Oracle)" , Jan Kara Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20261029-bug-mm-shmem-undo-batch-v1-1-59b34212fe78@gmail.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: <20261029-bug-mm-shmem-undo-batch-v1-1-59b34212fe78@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/30/26 04:44, Qiliang Yuan wrote: > truncate_inode_pages_range() takes the folios it finds out of the page > cache with delete_from_page_cache_batch(), which takes the inode's > i_lock and the i_pages lock once for each batch of up to > FOLIO_BATCH_SIZE folios. > > shmem_undo_range() calls truncate_inode_folio() on each folio instead, > so filemap_remove_folio() takes and drops both locks once per folio. > Truncating, punching or freeing a tmpfs file or memfd made of small > folios, such as a large /dev/shm segment, pays for that on every page. > > Clean each folio up as truncate_inode_folio() does, collect the ones to > remove and take them out with delete_from_page_cache_batch(), which > needs truncate_cleanup_folio() outside mm/truncate.c. Swap entries, and > the folios kept when undoing a failed fallocate(), stay out of the > batch. Dropping an 8 GiB file of 4K folios, median of five runs, > averaged over two boots of each kernel, in a 32 vCPU VM: > > before after > ftruncate() to 0 1163 ms 913 ms > hole punch 1155 ms 914 ms > close() of a memfd 1161 ms 914 ms > unlink() 1162 ms 916 ms > > Files of PMD-sized folios take 20-25 ms with or without this change. > > Signed-off-by: Qiliang Yuan > --- Doesn't look like something earth shattering :) I'll wait a couple of days for more review and will then pick this up. -- Cheers, David