From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 B7CDB45DF71 for ; Mon, 7 Sep 2026 10:42:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788777744; cv=none; b=Rmm7/J2+PBwBWQJZNrNSLbrXuxhgTM/O1sZN3Xcr7jLGg3+nuPwxLicnJI78iXwCwsDD56Vw24hc6rCFe9CmA0EeBX54EDTmYFwSlRydkHkaBrMx3gE0Te7axrRrkvrphGGmFzzkKd7qKcjZ5lLe2Ns9aOEEwlWiTUKyKIWodgQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788777744; c=relaxed/simple; bh=Ov3De7JjU7e3V3diQ4Ls9yEglALp8Bt5G62OHXmFufA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Hp0U1BNCutFxispekqtGoaBjzBfZkrnJyVM2bNfySJoNG7HM5mpboSexn49sDuDVeHwBG7/Z7eh00ovKUtXCyhTA8IHjbjED367PBAhHt4+r2GntGXl3KR4a8rtL6D35AkNTE85c1RUe9GlLtU7EaokO4Pi8MAKd76EL5sAlTwY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=c2/bMEep; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="c2/bMEep" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 336CB1F00A3A; Mon, 7 Sep 2026 10:42:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788777740; bh=bv3lOK+Xa5ryV284dRZSnT9zLzqTU49TaIVbEbCvDks=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=c2/bMEepc1j83amckC2cQIkOIRnCap+Llqh6TjNjeiVKdf7NB9ss/945JvVIokhbb IukLI0/YTu6RxrAhUVpbsG0XjGqmfVLnSWzSDNCoQjgzbk3LsMpl9zTdzw+4NzXv8Q ccoxpfmjtqELVXTvaWf2OqhptHwpy8jH+8FQ0rDoeyqtIGGfme2m0IHdDbfs/r7NJD rIiKgVV6ONvaLTJyzd1dDWerZbKiB502T5UkKY2bwWEoPDFjH8KpmECFKN6E6E9iEe KnAQSTUhY4Zmjpi48FUyoqVRESlKYxNM5ub1HmHySmcceSCH2Ia8m7Gtxg7DnfI5Uc Cz749Db8BmCcw== Message-ID: <616f0e6b-178c-4b50-b759-ccb20d9db9f4@kernel.org> Date: Mon, 7 Sep 2026 12:42:12 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm: thp: restore SHRINKER_NONSLAB on the deferred split shrinker To: Qinyun Tan , Andrew Morton Cc: =?UTF-8?Q?Michal_Koutn=C3=BD?= , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Johannes Weiner , Yosry Ahmed , Nhat Pham , Chengming Zhou , Kairui Song , Shakeel Butt , Xunlei Pang , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260904033503.4067283-1-qinyuntan@linux.alibaba.com> <20260904033503.4067283-2-qinyuntan@linux.alibaba.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: <20260904033503.4067283-2-qinyuntan@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 9/4/26 05:35, Qinyun Tan wrote: > On a system booted with cgroup.memory=nokmem, the deferred split > shrinker is quietly demoted to a non-memcg-aware one. As a result, > partially unmapped THPs are only split under global reclaim; memcg > (limit-induced) reclaim never splits them, so a cgroup under memory > pressure keeps its underused THPs intact. > > This is a regression from commit fafaeceb89a5 ("mm: switch deferred > split shrinker to list_lru"), which re-registered the shrinker without > SHRINKER_NONSLAB. The shrinker had carried this flag since commit > 0a432dcbeb32 ("mm: shrinker: make shrinker not depend on memcg kmem") > precisely so it would keep working with kmem accounting disabled. > Without the flag, shrinker_memcg_alloc() fails with -ENOSYS under > nokmem and the shrinker loses its memcg awareness. > > This was noticed by Michal during review of the patch "mm/list_lru: > don't copy stale shrinker id from non-memcg-aware shrinkers" [1]. > > Restore the flag. > > [1] https://lore.kernel.org/lkml/697713c4-0857-485b-aba7-c74f37a3c8b4@linux.alibaba.com/ > > Fixes: fafaeceb89a5 ("mm: switch deferred split shrinker to list_lru") > Suggested-by: Michal Koutný > Signed-off-by: Qinyun Tan > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David