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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Shuah Khan , Randy Dunlap , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Brendan Jackman , Johannes Weiner , David Laight , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: stop recalculating min_free_kbytes once set by userspace Date: Wed, 14 Oct 2026 16:34:56 -0400 X-Mailer: MailMate (3.0r7032) Message-ID: In-Reply-To: <20261014140859.1006967-1-noren@nvidia.com> References: <20261014140859.1006967-1-noren@nvidia.com> Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-MS-Reactions: disallow X-ClientProxiedBy: SA0PR11CA0039.namprd11.prod.outlook.com (2603:10b6:806:d0::14) 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_|BL4PR12MB9723:EE_ X-MS-Office365-Filtering-Correlation-Id: d0742dfe-0f42-4149-0d3e-08df2a329eb7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|366016|1800799024|7416014|376014|6133799003|10067099003|18002099003|22082099003|261009223027099003|11063799006|56012099006; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?LHiRH8xTWSKMYBvCc/oKtgmeBYKXHBJPnBd2oBv1vkRHNZJOe3ybIdnBXzi6?= =?us-ascii?Q?7vNcLfKIoic7SjvY2bKMuXEktG+y7TuSIqVfKvNB0K9duPx2xPJ1LLkab7uB?= =?us-ascii?Q?Iqby07QfSY59ObhGICKoTWPogSWLSzVAKi9icUkdzifa0BXjSluuecgXl+fv?= =?us-ascii?Q?vMZ55lTzAivOM+UUhqUKGChZB9K3NVxEmI/ji+O+AFQoPU0W49eCuukphiFT?= =?us-ascii?Q?xyCSfkyjHvTRrHqYTWnzyVUbUlrbMaGWPo4m1nENhNOn63OKc82c3TEok1Ue?= =?us-ascii?Q?fPTjGpouxsqKPATRc3J6JdQikMbEKPw4QjNUo1hIhEyTwq4f6LQHMVmIrjUw?= =?us-ascii?Q?jvrrFwEqqd3vmQGNXuhxMN/8toLgGLXFxrKNFUlNYRLab9bkJw4cH2RBsh3g?= =?us-ascii?Q?qhBMjCkBwQaM1e3KV3Rxj4V+6KgGjcLAsgCYoxHmHDjxeBtzNSCDtBvRIETd?= =?us-ascii?Q?5gyrrMXCDkQiQQBfcGDCG93SxwevwH/AopOa5uYmsgpdK/18m8JrMqQZjtjK?= =?us-ascii?Q?pcpm0EZ+3sgNHEvEos2kSzcUZZiJqAlG2uOpyJh63nFjEEKvvCEj7H9q99Kn?= =?us-ascii?Q?I3VjMALOR1gXR7xwUZF0qHqmoRpD9nRFndYE3wLaJW6+Be8ihiVM3+jpjVGV?= =?us-ascii?Q?8n1Yqg/pweOQhrDbZeECQyIZ22Vp6YI3oRcF96uIyUGyF3WLTS4feRYyDSes?= =?us-ascii?Q?iYYGtLv4oFH3WjBbnMaaLANArtti3uQ8p7dogQ83/pKJw8bRno5C8qWEdaD+?= =?us-ascii?Q?kHgQqhefL9qL64+heZTDUvYb7kJOSmQP3LlNoQJhBlLwXE1ND+zGpwwEfKql?= =?us-ascii?Q?WlFP6qDGOnOEp6d7E49iRQVUv61uy+aSVMmFMG2GPAb5p9l/WSXkUpIR908H?= =?us-ascii?Q?P3uIVxcyDjxzBKqV7ZZIkhMwti/m5A+RGYDWFfVnHigNm3t8oGBT/FbwViix?= =?us-ascii?Q?EE/mtllfxc5kpNZyLX3qOpNFEjwVNwr9+wr8hv8WV/IAfjyaMGAg7Us0+Yvw?= =?us-ascii?Q?lmR4nzJuyHgPWyq6p5+ypJatbz2kNA07XEjC7T14rFzz9mb3dqAaHcNKmHAT?= =?us-ascii?Q?R/zM822kJlGtEB13aVjPYR+wo7qwa5MGnReHCEzQcfqEM1xZ6AopVKCOi3vL?= =?us-ascii?Q?USsHwaiiQGwWfKUi/o+i0NPMcxDaIJvcs0zZ6rfXbxpBhPDiHX+fJ+n0hv7D?= =?us-ascii?Q?fjacxeYBKpvLG+rMgjLFh/riA4wexoLmsYwXV5jNv9Bm2mEc7nyYXhW4xWIZ?= =?us-ascii?Q?JVtm/ujE2iKNJCuef+hZqTFZ3PWUn7ZIZaR/KPcTF9JYg1PnJMw6oRS1DOjr?= =?us-ascii?Q?u5/ubcEYQTKXFlUxOigiPCIsDfFyS7Sfu4Lt665D68TnPX5buzXFMdgMpzuh?= =?us-ascii?Q?NDyvI9rrBzdyXwTm4r/Ft+Gbx5EVPm2ddkn/mPHpLye3HmbMUslAR2wDnEdP?= =?us-ascii?Q?5d0PTK4tEUMka2CB7KfK5Au3lQtVtJyX1a6Pewj/lrXk2nT9MiBucm2DOqWz?= =?us-ascii?Q?KtQDBPhZL01kC9Mfby+36yNCoa0yWYGlPmR9FW3UXeAHJp7KqL9fMImOpI8Z?= =?us-ascii?Q?Lr0JSQyU7GWBsWgG0WytT/LfyFBzlFOFBDGueEaEi/43INZk1QilMCWcccKo?= =?us-ascii?Q?S03ZafZ/PBL0XBKc/o8Ws90meJeXKjcmOSGHX1e3P0VoqB/p1kZ+nbbU2Ul3?= =?us-ascii?Q?+TN0FfNxKmZU0MIudDab0ycVvmJHHtuoQFtI1zeykDZro4wi?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: d0742dfe-0f42-4149-0d3e-08df2a329eb7 X-MS-Exchange-CrossTenant-AuthSource: IA0PR12MB8374.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Oct 2026 20:35:01.1801 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Il0gHHonPeYwwooKpwhFu5og4uduNTvIs6IOyn19cbRWrOcrXqFB8UyfUNs7yIEf X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL4PR12MB9723 On 14 Oct 2026, at 10:08, Nimrod Oren wrote: > min_free_kbytes is recalculated on memory hotplug and on THP sysfs > writes. The new value comes from calculate_min_free_kbytes() or, while > THP is enabled, from set_recommended_min_free_kbytes(). A value written= > to the vm.min_free_kbytes sysctl is replaced whenever the new value is > higher, so a lower value does not stick. This matters most when THP is > enabled on configurations with large pageblocks, where the new value > can be excessive [1]. > > Stop recalculating min_free_kbytes once a value has been written to the= > sysctl. Systems where the sysctl is never written keep the current > behavior. > > Link: https://lore.kernel.org/r/20260716173504.760369-1-noren@nvidia.co= m/ [1] > Suggested-by: Vlastimil Babka (SUSE) > Link: https://lore.kernel.org/r/d202dcc3-d7d7-4e98-a9a5-3137cfbfd041@ke= rnel.org/ > Signed-off-by: Nimrod Oren > --- > Documentation/admin-guide/sysctl/vm.rst | 7 +++++++ > mm/khugepaged.c | 7 +------ > mm/page_alloc.c | 6 +----- > 3 files changed, 9 insertions(+), 11 deletions(-) > Acked-by: Zi Yan Best Regards, Yan, Zi