From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A5F4D277C9E; Thu, 16 Apr 2026 08:47:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776329238; cv=none; b=lpdYerP9MKPzF8Sy8ApuISup0GdV78OMKjNXr1MPrNg74ySbo5EIbWfNn6I3bGu3BJSqbPTcbvxU87zwIwr6+64STWVKKBKzfNNSqrm6UnChv1te5sbTDq/KLaCzpjIkkUgiFS7H71Z8cnIfXfjJXBl/d3FR2e2Cp2Cp3z9LCw0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776329238; c=relaxed/simple; bh=ljHxmoprfBQIb7mZOQd9Nqr851XmhOqAdzFFK3AVVB8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sqpZMslEXaaMIgtWhHZpdr1rsd/5lLulY7sPci+sxpwh3dlcRYGqgcPdOFvkFDsquHlZJ1sLioiIWu4fHSD3GzRObRz1TnBb30WmnaBGM6QxkuKhXn/b+DzGMPxwtt+cNJqVJIHuWX7KxOs+yAVOP8V4hjv9fmKGi6JoZghvW6U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=OoR+cLLp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="OoR+cLLp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 236FFC2BCAF; Thu, 16 Apr 2026 08:47:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776329238; bh=ljHxmoprfBQIb7mZOQd9Nqr851XmhOqAdzFFK3AVVB8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=OoR+cLLpx1ccGF8jHeCIEO2WG0KmtE7gfcMfcszVO2ap0qzWDPGRaOzUF7ry7egHn Nu9ZzjXLV5ep+/DQ7VRURFa0r6t8qXmr40PjYDKsdFcleR6S/Ws4j8UptbKPH5c/LW 0l8bRYlXgZwLbncZ6FZfDX68tvs5tolPPvGxWyDo/5ZXO4HwtpyxV6IJnaVQAzyp7t oSlic8y4ay5jx+bjaoa1wnGln8rP/e65WEuRERPVXkvOmYR1CPz1S/A+aDNjjQSjSK 8SqmC7DUl0w+XbDv78koqFD+ifY5f3Jy01Lz75H0f4/BYDTPM6tdVmlnL7t90HCPbS A1NUFh4DOZF/w== Message-ID: <8d95a9ad-4c85-4b8e-8724-af843e1b7859@kernel.org> Date: Thu, 16 Apr 2026 10:47:05 +0200 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 , Baolin Wang , Matthew Wilcox Cc: Nico Pache , Song Liu , Chris Mason , David Sterba , Alexander Viro , Christian Brauner , Jan Kara , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , 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> <84B8F641-A3DF-4219-AA57-6BA48E9B4998@nvidia.com> <998c02b6-2612-42c1-8099-d65ae275d1a2@kernel.org> <7468C68E-FB09-4714-94A3-4BED63453295@nvidia.com> <38697379-cbba-4c64-ae65-6774b01021d9@linux.alibaba.com> <68F85F77-8EFE-449D-B643-AEEB38CB50B2@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: <68F85F77-8EFE-449D-B643-AEEB38CB50B2@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 4/15/26 20:01, Zi Yan wrote: > On 15 Apr 2026, at 5:21, Baolin Wang wrote: > >> On 4/15/26 4:00 PM, David Hildenbrand (Arm) wrote: >> >> My comments are in reply to Zi’s comment: >> >> "I think hugepage_global_enabled() should be enough to decide whether khugepaged should run or not. " >> >> I’m concerned that only relying on hugepage_global_enabled() to decide whether khugepaged should run would cause a regression for anonymous and shmem memory collapse, as it ignores per-size mTHP configuration. >> >>> The question is really which semantics we want. >>> >>> Right now, there is no way to disable khugepaged for anon pages, to just >>> get them during page faults. >> >> Right. >> >>> And we are now talking about the same problem for FS: to only get them >>> during page faults (like we did so far without CONFIG_READ_ONLY_THP_FOR_FS). >> >> OK. I’m fine with using hugepage_global_enabled() to determine whether khugepaged scans file folios. >> >> My concern is that for anonymous memory and shmem, the per-size mTHP settings should be considered. > > OK, I misunderstood the meaning of hugepage_global_enabled(), since per-size > mTHP settings could also enable khugepaged if PMD_SIZE is set. > > I will take willy’s original suggestion and make khugepaged on if the global > setting is enabled. The below is the new version of this patch. I moved anon > pmd huge page code to a separate anon_hpage_pmd_enabled() like > shmem_hpage_pmd_enabled() and cleaned up the comment. Let me know your thoughts. > > Thanks. > > From 92b92f2b2ab41c70b41dd304ce648786ee6a1603 Mon Sep 17 00:00:00 2001 > From: Zi Yan > Date: Wed, 15 Apr 2026 13:52:50 -0400 > Subject: [PATCH] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check in > hugepage_pmd_enabled() > > Remove READ_ONLY_THP_FOR_FS and khugepaged for file-backed pmd-sized > hugepages are enabled by the global transparent hugepage control. > khugepaged can still be enabled by per-size control for anon and shmem when > the global control is off. > > Signed-off-by: Zi Yan > --- > mm/khugepaged.c | 26 +++++++++++++++----------- > 1 file changed, 15 insertions(+), 11 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index b8452dbdb043..586d27ce896e 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -406,18 +406,8 @@ static inline int collapse_test_exit_or_disable(struct mm_struct *mm) > mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm); > } > > -static bool hugepage_pmd_enabled(void) > +static inline bool anon_hpage_pmd_enabled() > { > - /* > - * We cover the anon, shmem and the file-backed case here; file-backed > - * hugepages, when configured in, are determined by the global control. > - * Anon pmd-sized hugepages are determined by the pmd-size control. > - * Shmem pmd-sized hugepages are also determined by its pmd-size control, > - * except when the global shmem_huge is set to SHMEM_HUGE_DENY. > - */ > - if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && > - hugepage_global_enabled()) > - return true; > if (test_bit(PMD_ORDER, &huge_anon_orders_always)) > return true; > if (test_bit(PMD_ORDER, &huge_anon_orders_madvise)) > @@ -425,6 +415,20 @@ static bool hugepage_pmd_enabled(void) > if (test_bit(PMD_ORDER, &huge_anon_orders_inherit) && > hugepage_global_enabled()) > return true; > + return false; > +} > + Works for me. > +static bool hugepage_pmd_enabled(void) > +{ > + /* > + * Anon, shmem and file-backed pmd-sized hugepages are all determined by > + * the global control. If the global control is off, anon and shmem > + * pmd-sized hugepages are also determined by its per-size control. > + */ > + if (hugepage_global_enabled()) > + return true; > + if (anon_hpage_pmd_enabled()) > + return true; > if (IS_ENABLED(CONFIG_SHMEM) && shmem_hpage_pmd_enabled()) BTW, can we please provide a stub for shmem_hpage_pmd_enabled() in shmem_fs.h such that we can remove the IS_ENABLED here? -- Cheers, David