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Tue, 5 Aug 2025 21:15:52 +0000 Date: Tue, 5 Aug 2025 14:15:49 -0700 From: Matthew Brost To: David Hildenbrand CC: Balbir Singh , , , Karol Herbst , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , =?iso-8859-1?B?Suly9G1l?= Glisse , Shuah Khan , Barry Song , Baolin Wang , Ryan Roberts , "Matthew Wilcox" , Peter Xu , Zi Yan , Kefeng Wang , Jane Chu , Alistair Popple , Donet Tom , Ralph Campbell , Mika =?iso-8859-1?Q?Penttil=E4?= , Francois Dugast Subject: Re: [v2 01/11] mm/zone_device: support large zone device private folios Message-ID: References: <20250730092139.3890844-1-balbirs@nvidia.com> <20250730092139.3890844-2-balbirs@nvidia.com> <1e307223-897c-4db0-9564-95d76bc3d260@nvidia.com> <98a30c7f-8be1-4b08-955c-724667971288@redhat.com> <9c0ad782-e1c3-4c7d-bb20-730d2f915dd5@nvidia.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MW4PR03CA0092.namprd03.prod.outlook.com (2603:10b6:303:b7::7) To PH7PR11MB6522.namprd11.prod.outlook.com (2603:10b6:510:212::12) 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: PH7PR11MB6522:EE_|SA3PR11MB7486:EE_ X-MS-Office365-Filtering-Correlation-Id: 6ac1c86f-7d53-431b-7915-08ddd4654237 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|7416014; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?b+vUo52cExNfcOlSMK05CxtF/mGD65GrDLkpxQ5p0lrZss/ze+zKZaWFmfqK?= =?us-ascii?Q?Gqsv8O3NjU6ui+bhudiJtfDDXjGFw/A4a0ju461S9EsHF7OubS6RS0WPxdFM?= =?us-ascii?Q?zz2f4SciFMUhDzsr9WKkEITANSBjhJDJFBIb+o8iH3gbbqaV1+g5s3xRtFPV?= =?us-ascii?Q?K3sANon9NZuuM7n5l/VF96EYvJyauP0yGPglKj7HQRwX9uaI4gx6A6Mad/7+?= =?us-ascii?Q?YrZ/NA4jhnc2XoGYKWGTKxz3PIKRMpseiMUzji3qJXMJsHG6lJZr8W3Ya5+h?= =?us-ascii?Q?3RlMsHD0tUpb43M+w1a+UIm9UHU/S15lgQC0HtKXhLKmEFZ5e+9Tt1M5Vy1Y?= =?us-ascii?Q?8AlmAAZHDXbofHlplMCEbYCKDnXAr80Y3tHrKmJTE7DsBv2ekhb1y1f3PRxz?= =?us-ascii?Q?MVFjRkXKldePnlHIIwAOh8vn+qq0SZVrB/Un57ISg36pDJwIYx9nchztwB51?= =?us-ascii?Q?cpi/lfh3IeqbDAMzqboa6Oov+uCuRrQf3buy9+c7aPGmqIWdkLI9hw7KUdfH?= =?us-ascii?Q?DoaRCR78KJA5JBhTVYJZAZp4QebT2Da3Bd/ttCE3mFTSVJ0l81e5fIwLdl/y?= =?us-ascii?Q?HXLpjH35AV6G8imuN1e5obY6ph//sTn8RGgwKznBVEOvn0OxwbBJlZG+4KTV?= =?us-ascii?Q?mEFDTmM5Mzaq3GSVikkA8xxtJPDYWPjbd1F/KC9RkmY/i8yQ7IJJe+a+SK1l?= =?us-ascii?Q?kGhrLoGJliEzeJrNxsFbcrN/B/Gn8Bgaaw7Fq0QdaWL5MrYHkpiMY7pO58pV?= =?us-ascii?Q?qoepH3tMlDtQgOxMFgdRLmnNzYclJqryv7ubidrKrUaoMxAvQfqse0+qjg44?= =?us-ascii?Q?YlNo1QrpDFAyg5xW5zog8kdPg+dP/SQcWyuZi9rZOFN/8/VCKaMIPKBD6+4P?= =?us-ascii?Q?UtQF6yQJNdVfN0bwAUEknH1CrO4dvl++DRXUWaKBLpbKjleFiiHNKKN3Kn4z?= =?us-ascii?Q?hxyWNSf9bggcF6dYyvPYj6nU224SeMq3t4yLuIu+K6F3jgtrT/v173PMKtNw?= =?us-ascii?Q?pmCIcs1cBCGzZHajzbdgLLILqLi7LDzyB5LEE6hARMuLPZd0GTel4vMpSTjU?= =?us-ascii?Q?0jswykw646ppAO1L1VSIZnXj+FriyQ0/lxlR2YMmlACpskbZvci5Zy4uO2ZE?= =?us-ascii?Q?YrlqYTRTd/WTRzmyr/QeZObhnFxj9MDSf5tG7fXjhiCZiQLRxTAFZPnWBBcm?= =?us-ascii?Q?nihDHQACPBdLeqAiWdFxQRfV2W024ROV8u6nOGtmJjkdgYwXZYC98lqcZmry?= =?us-ascii?Q?XRgl1yDEc29lSWphuKRnw0NNC+XzoSp8VWpF+gu7RxPdy0oFdHIzRbbv4CQ3?= =?us-ascii?Q?EA01tJT+Uw8RYLVNX0O0ZtsmUqn/iHwkGUzVYlIYujqD1mCRYvB5gqN1flx+?= =?us-ascii?Q?6/K8aG6/j41AH0pAK7/7Nfp6X6WgKzHUUutnUGh1ICeaGaylwdb8vtgPTe44?= =?us-ascii?Q?XMSrTLuuRm3Y4etGk+beeQlamQmZezTWBPqtaPTAOgUjtwFFSOfUrZwI8t4M?= =?us-ascii?Q?8D5V94UqG/Bu+07a23S5ZQqz8a4Y6b+5UMFn6wOvsO/I52t3AZT0mil3iMCt?= =?us-ascii?Q?y6EGP6ybzB0t2qXT8APSGEFEzzaPZuEuK2to6ycwXXyj/FDCv9OghR55PB1D?= =?us-ascii?Q?Lg=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 6ac1c86f-7d53-431b-7915-08ddd4654237 X-MS-Exchange-CrossTenant-AuthSource: PH7PR11MB6522.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Aug 2025 21:15:52.6002 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: aMY2pDyPE5YeZC+JBCxO2qgm3pb8rO862LYqo/I7pENOoFSkgKy1o+fQurH88slgXddb1sqwhdkXvsbaqSXe7A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR11MB7486 X-OriginatorOrg: intel.com On Tue, Aug 05, 2025 at 02:58:42PM +0200, David Hildenbrand wrote: > On 05.08.25 13:01, Balbir Singh wrote: > > On 8/5/25 20:57, David Hildenbrand wrote: > > > On 05.08.25 06:22, Balbir Singh wrote: > > > > On 7/30/25 19:50, David Hildenbrand wrote: > > > > > > > > > I think I asked that already but maybe missed the reply: Should these folios ever be added to the deferred split queue and is there any value in splitting them under memory pressure in the shrinker? > > > > > > > > > > My gut feeling is "No", because the buddy cannot make use of these folios, but maybe there is an interesting case where we want that behavior? > > > > > > > > > > > > > I realized I did not answer this > > > > > > > > deferred_split() is the default action when partial unmaps take place. Anything that does > > > > folio_rmap_remove_ptes can cause the folio to be deferred split if it gets partially > > > > unmapped. > > > > > > Right, but it's easy to exclude zone-device folios here. So the real question is: do you want to deal with deferred splits or not? > > > > > > If not, then just disable it right from the start. > > > > > > > I agree, I was trying to avoid special casing device private folios unless needed to the extent possible > > By introducing a completely separate split logic :P > > Jokes aside, we have plenty of zone_device special-casing already, no harm > in adding one more folio_is_zone_device() there. > > Deferred splitting is all weird already that you can call yourself fortunate > if you don't have to mess with that for zone-device folios. > > Again, unless there is a benefit in having it. +1 on no deferred split for device folios. Matt > > -- > Cheers, > > David / dhildenb >