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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" , , To: "Qinyun Tan" , "Andrew Morton" From: "Zi Yan" Subject: Re: [PATCH 1/2] mm: thp: restore SHRINKER_NONSLAB on the deferred split shrinker X-Mailer: aerc 0.22.0 References: <20260904033503.4067283-1-qinyuntan@linux.alibaba.com> <20260904033503.4067283-2-qinyuntan@linux.alibaba.com> In-Reply-To: <20260904033503.4067283-2-qinyuntan@linux.alibaba.com> X-ClientProxiedBy: YQZPR01CA0037.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:c01:86::7) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA0PR12MB8374:EE_|DS0PR12MB8502:EE_ X-MS-Office365-Filtering-Correlation-Id: 618a0a19-8437-4a18-f633-08df0a979844 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|23010399003|1800799024|366016|11063799006|10067099003|4143699003|22082099003|18002099003|56012099006; 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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@lin= ux.alibaba.com/ > > Fixes: fafaeceb89a5 ("mm: switch deferred split shrinker to list_lru") > Suggested-by: Michal Koutn=C3=BD > Signed-off-by: Qinyun Tan > --- > mm/huge_memory.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > Makes sense. Acked-by: Zi Yan --=20 Best Regards, Yan, Zi