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 B6558ED7BBE for ; Tue, 14 Apr 2026 11:02:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D38A16B0088; Tue, 14 Apr 2026 07:02:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CE92D6B008A; Tue, 14 Apr 2026 07:02:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BB1486B0092; Tue, 14 Apr 2026 07:02:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id A59946B0088 for ; Tue, 14 Apr 2026 07:02:16 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 3A12816057E for ; Tue, 14 Apr 2026 11:02:16 +0000 (UTC) X-FDA: 84656872272.19.6DF7B20 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf07.hostedemail.com (Postfix) with ESMTP id 7D61D4000B for ; Tue, 14 Apr 2026 11:02:14 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=NfrtkX74; spf=pass (imf07.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=1776164534; 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=qn1bffZjR8CmDbnWwb2oX+/5tlIhWeRe7bJKU6Ignjg=; b=T9aaXPdAnsMaKbTUDuxu0lwh09oScZf1pSQqC++sSq8R1LaHMHasTpfogntRl/6nZCOfwJ 34zHZDLJBuKLCFuhaxTR7ZM0v2zlMGIleP2fRB5iUEEkn6ni+t6kVd8t+PwgFDlYxTElXO YzuwI9Vfo/MCjB/NaeshkYWQ4N4IYaY= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=NfrtkX74; spf=pass (imf07.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-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776164534; a=rsa-sha256; cv=none; b=FoRie3VqH4ByQXsc0vo/SavmlR1r8QRxPChCuqTyFFzECFbzQhdR0wCqWdwvsnMxc9Q4Vf 7QLrx+otRksiHL6txNYPldlexDmxjR39g9Rd5jhtKcbEZSpBLwlO+bloDvbXDx23HxDWeG mkILPa3G8PLBPS9/LzSTPOr73webIko= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id D75356011F; Tue, 14 Apr 2026 11:02:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92A6DC19425; Tue, 14 Apr 2026 11:02:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776164533; bh=3pzMZMfMkr/IcuqUWA3o3NMItdA227VUY7ANJl/0BFs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=NfrtkX74P0KKHje61gprd/J6K00bTdrDkBqxS4bMicEwRhHRqJmr/MIBHFi059xyZ 9Nn4IbiL3DtTnBSsdyPa1YJJUsjrCw2R6T3DuulETl6gzTFaD1Y0VyI/ovgpryfF/o kHLaibZ8LVCz6RgHsz3MlnqTYu6sKe3JWouz24qxN9ypDUqdMKi8Y8l39kaWMZTcdt lhrJ6+kunkGflPirnUc0V6A1U/coHeRoDiTCn0Tnb/jqvzq/OUDrMWxlNxjEyhHbG+ HxAS4YEy/mcvYjZu6np5TrwFbHoST+htmjVEHLaeJWLafcixeHpyEjgpPQk5EOgcZu a2s9DurQZtt8A== Message-ID: Date: Tue, 14 Apr 2026 13:02:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 7.2 v2 05/12] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check in hugepage_pmd_enabled() To: Zi Yan , Matthew Wilcox Cc: Song Liu , Chris Mason , David Sterba , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20260413192030.3275825-1-ziy@nvidia.com> <20260413192030.3275825-6-ziy@nvidia.com> <05F00072-7E06-47C9-BC26-FE3736F557FC@nvidia.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: <05F00072-7E06-47C9-BC26-FE3736F557FC@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 7D61D4000B X-Stat-Signature: pm3ujq58xr96ds7n4r3kfmabux5iiimz X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1776164534-147836 X-HE-Meta: U2FsdGVkX19O3ehPOXElBcGIcJb5bcMbAh3jmB7HuWrIQL5lxKuoKwOIeV3gFx0F9oME5Dx2WDlTDuuRtqG6eJID0+RfRmsLa2Zjs8glJ0MMGcg5aSbiYZwzynpuNSBuNoGJNtvarB7h/vORnb1HlJTfwsU78idBX1khioEJqiqXXFEpzi1DcS7yCpB54Q+gDz6clSni5V84y1ZaOoInRSonLaKvWmkyRLHWw7JgAxdJuLCdat2cCAhDL/gRP2viUvC7z82iKOemq2FoLmokB+dU/kb/E0Fmy6uJF1tv4wbRqHRCI/hiWxIBdDIseiypLaaLACAlJahq7TvQ8KQFVGaeq0jhtPpYpI1qx9Z9PTZurp1tKJ6W/q56ykEzQ12BmJePdtUfz/OhJViHLVrN5E/tpAGi9YuKueCunLb3/7aaUyNoAh8Wlb+yCnRhY6GyNarV5XnkfCoxQwLjHSdiPXynpJssgY2IoZXkq58MjvNa0cgV0bi5QewYL8UTgH4lUyCmtPgl5V2n8Rr4iRVmLAoPHb0cXMuek0rgOhrrQWydVbdvE2AoV3p9454clZzWDCjzUp9YD+CvliExS/k4RkOOnA5N0M4/uQPY+tsb5bLssk0PnOPsiah4+P0RXcvwPEcP8PVikzvLpFhLvsfoZMPpTJocy07Fpj+pvWeBj7st4JPetqLsW/TgvR8xeuMm8ZcRihmU1vCGU7F7HQj/qINOgT92ZwirHE9as2tCWbZLiPvlxXKw6jITqVQS++10NELL72BZ9XygEG+PBF+npyXaURh2lywGmGwnuJDJeBQJpVtefkRB+DGrBZIDTf+4LQfUmlemQHzz5jLeQ+Xv8Bfrtt4aeI0EA/lioBJmh5PT6RPhtWsMdut0EW3AUsYtOPsRS/G12gRE87bFZ6Xw+yZIjKSX1udTIlX4AH5LPstEunngX1AsFd1JM8UWm76CqhQ4ErRGqOAQzw520oO BHXGVLg9 PTA7fIjOzHGbfOFjxHAGMF9GqyIjkONZWzPdbjBpSwcr+tyU1U5azHsgotNNICdebupA5tvu+KaJCOX3zhkSmG5MXZZyHvRvPjcuw9mjhIachWeKV+o2oaa06hl4IHtWWLJK/i4L0DVTKCmeBPoqYEiAtmyRPNBx6P+ILNYb4pEkJ8XeYjTEAWZYdeC1go3cyVne74/bD4yX/Z8XJZ0jaWXk3E2zGjsdEdJsJqz95wtWqs5av41MAD6Y7L+qjQD21JBgbKa0qkFVZ96wW/fiRO2LgbXfi58nn2rijemv3vpyvnT6VSyfTMbI5QA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/13/26 22:42, Zi Yan wrote: > On 13 Apr 2026, at 16:33, Matthew Wilcox wrote: > >> On Mon, Apr 13, 2026 at 03:20:23PM -0400, Zi Yan wrote: >>> After READ_ONLY_THP_FOR_FS Kconfig is removed, this check becomes dead >>> code. >>> >>> This changes hugepage_pmd_enabled() semantics. Previously, with >>> READ_ONLY_THP_FOR_FS enabled, hugepage_pmd_enabled() returned true whenever >>> /sys/kernel/mm/transparent_hugepage/enabled was set to "always" or >>> "madvise". >>> >>> After this change, hugepage_pmd_enabled() is governed only by the anon and >>> shmem PMD THP controls. As a result, khugepaged collapse for file-backed >>> folios no longer runs unconditionally under the top-level THP setting, and >>> now depends on the anon/shmem PMD configuration. >> >> This seems like it'll turn off khugepaged too easily. I would have >> thought we'd want: >> >> - if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && >> - hugepage_global_enabled()) >> + if (hugepage_global_enabled()) >> return true; > I assume such a change should come before patch #4, as it seems to affect the functionality that depended on CONFIG_READ_ONLY_THP_FOR_FS. > I thought about this, but it means khugepaged is turned on regardless of > anon and shmem configs. I tend to think the original code was a bug, > since enabling CONFIG_READ_ONLY_THP_FOR_FS would enable khugepaged all > the time. There might be some FS mapping to collapse? So that makes sense to some degree. I really don't like the side-effects of "/sys/kernel/mm/transparent_hugepage/enabled". Like, enabling khugepaged+PMD for files. > >> >> ... or maybe this whole thing could be simplified? > > Alternatives could be: > 1. to add a file-backed khhugepaged config, but another sysfs? Maybe that would be the time to decouple file THP logic from hugepage_global_enabled()/hugepage_global_always(). In particular, as pagecache folio allocation doesn't really care about __thp_vma_allowable_orders() IIRC. I'm thinking about something like the following: diff --git a/mm/huge_memory.c b/mm/huge_memory.c index b2a6060b3c20..fb3a4fd84fe0 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -184,15 +184,6 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, forced_collapse); if (!vma_is_anonymous(vma)) { - /* - * Enforce THP collapse requirements as necessary. Anonymous vmas - * were already handled in thp_vma_allowable_orders(). - */ - if (!forced_collapse && - (!hugepage_global_enabled() || (!(vm_flags & VM_HUGEPAGE) && - !hugepage_global_always()))) - return 0; - /* * Trust that ->huge_fault() handlers know what they are doing * in fault path. Then, we might indeed just want a khugepaged toggle whether to enable it at all in files. (or just a toggle to disable khugeapged entirely?) -- Cheers, David