From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C9FBCFD5310 for ; Fri, 27 Feb 2026 08:45:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F21C46B0005; Fri, 27 Feb 2026 03:45:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id ED4456B0088; Fri, 27 Feb 2026 03:45:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DCD8F6B0089; Fri, 27 Feb 2026 03:45:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id C8C4D6B0005 for ; Fri, 27 Feb 2026 03:45:19 -0500 (EST) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 536711B796C for ; Fri, 27 Feb 2026 08:45:19 +0000 (UTC) X-FDA: 84489602358.08.2301195 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf01.hostedemail.com (Postfix) with ESMTP id 98F0A40002 for ; Fri, 27 Feb 2026 08:45:17 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=lEGAfAq9; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1772181917; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=bROheX+CGuYoF3pyuyZ7Xe0Ef08TUwZy1bB2PjiNHkY=; b=B7fSFQPkNoKE+MTiGdSFp4hm2Kq1FbI4Har2IEg60ZZFjCCrUq0hbqmXYz82XakKntQ7sO sxziDhs2eTzxET6qJDM2dy7LjRJfqHTm6e6gYXm8FiwbUzj1teB425WnZ+dDUF0UPF5Kwr BcpBczPchPgcb3oPkkkUNQ3x48BfUI8= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1772181917; a=rsa-sha256; cv=none; b=hbNwQuekKzn3KS2p1LSxawC/zVL8kzV0zpZaPGc783P7FzMlXnxeILJPfTK3AZ9MR+zH4I T0Jn2DNDO8QwyG8qpXEospt8jDy29X58Y5xDLSNs00V2UNLCYL4N4QoTFTJ1+w1m/UzyHI 0xe6ejWmREoBRTdB+MqMFb8BNLyMpQI= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=lEGAfAq9; spf=pass (imf01.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id B483C60008; Fri, 27 Feb 2026 08:45:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CBE0BC116C6; Fri, 27 Feb 2026 08:45:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772181916; bh=M3wiUV92iKKp8CgWC8J6GoLftiC/em8BQZ0MsIGSMhk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=lEGAfAq935TU0KRtBBEWHVxzGrMa5zoqShGP8N9yO5S9/gmcV2y+tC+Tz0zPyvBNy 3cQyjoyFvIFs1738k5ViVxk6RttUCy2/yS2qC772eQRbRI/fwoYOMQ/ih0J6PgV1o8 Isu4cXQ4dh20jgdgFReFILFJ8wkKe+t3uWi4qK/vJMHtSi3vO92utzg2/PMbkSGYPA N1EzOq9Aj44UIr8INxTuHHDN1efAPeB1WW3s7M6Gcg1O6/nOjFGkBFN1DWQacC7By1 bvexOIZIsTvoqRsw4U1XrxeeQDyN59dZ51q8Yg5wsEmBvXqLLoJh70EYIt9IP83qS4 nwnA108U1fN4g== Message-ID: <8ca84535-861c-4ab0-a46b-5dfe319ac8ac@kernel.org> Date: Fri, 27 Feb 2026 09:45:07 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC v2 0/3] Decoupling large folios dependency on THP To: Matthew Wilcox , Pankaj Raghav Cc: Suren Baghdasaryan , Mike Rapoport , Ryan Roberts , Michal Hocko , Lance Yang , Lorenzo Stoakes , Baolin Wang , Dev Jain , Barry Song , Andrew Morton , Nico Pache , Zi Yan , Vlastimil Babka , "Liam R . Howlett" , Jens Axboe , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, mcgrof@kernel.org, gost.dev@samsung.com, kernel@pankajraghav.com, tytso@mit.edu References: <20251206030858.1418814-1-p.raghav@samsung.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-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 98F0A40002 X-Stat-Signature: 1taykt8jgqh73h4mp16mwr4qpq53csxu X-Rspam-User: X-HE-Tag: 1772181917-144394 X-HE-Meta: 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 1LxBAEws QpO5kfAqYZ9Gl4ZJLHaU/huqPmFfaY6qKkQm5hZQmxe11TI3iXlk2iW/ktap+eXOXww0eOAQTFyoFxzWDC5cXmfhnjstzxoLfkcZlluc4QDRZy91RAexTwXvAxKKpjat2vAlFtMohULJTjqe+E/5SOD7RNGeHn3MihnEcTEnmRnXiXM6vo4fhJ3NJ3NWXPewF5wnx3+Ay5Fr5Sui4yjD34D+P01y2xO2tZS4/+faePv7B7kcgC4S6zAKhWxGt7+NPNY76 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/27/26 06:31, Matthew Wilcox wrote: > On Sat, Dec 06, 2025 at 04:08:55AM +0100, Pankaj Raghav wrote: >> There are multiple solutions to solve this problem and this is one of >> them with minimal changes. I plan on discussing possible other solutions >> at the talk. > > Here's an argument. The one remaining caller of add_to_page_cache_lru() > is ramfs_nommu_expand_for_mapping(). Attached is a patch which > eliminates it ... but it doesn't compile because folio_split() is > undefined on nommu. I guess it would be rather trivial to just replace add_to_page_cache_lru() by filemap_add_folio() in below code. In the current code base that should work just great unless I am missing something important. > > So either we need to reimplement all the good stuff that folio_split() > does for us, or we need to make folio_split() available on nommu. folio splitting usually involves unmapping pages, which is rather cumbersome on nommu ;) So we'd have to think about that and the implications. Could someone stumble over the large folio after already adding it to the pagecache, but before splitting it? I guess we'd need to hold the folio lock. ramfs_nommu_expand_for_mapping() is all about allocating memory, not splitting something that might already in use somewhere. So I folio_split() on nommu is a bit weird in that context. When it comes to allocating memory, I would assume that it would be better (and faster!) to a) allocate a frozen high-order page b) Create the (large) folios directly on chunks of the frozen page, and add them through filemap_add_folio(). We'd have a function that consumes a suitable page range and turns it into a folio (later allocates memdesc). c) Return all unused frozen bits to the page allocator -- Cheers, David