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Shenoy" , "Ingo Molnar" References: <5cdf379c-b663-424d-8505-d91046e63c20@amd.com> <0a81b5be-6edd-4231-859b-0c6d06c61595@intel.com> <2c57d76f-fb31-4e1b-a3ce-ca13713e1b86@amd.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF000044A3:EE_|DM6PR12MB4201:EE_ X-MS-Office365-Filtering-Correlation-Id: bc0b51fb-b5c5-4244-1e68-08de176b910e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|32650700017|36860700013|7416014|376014; X-Microsoft-Antispam-Message-Info: =?utf-8?B?UXY1WlZYSGc2eTI4dWN2ZHgrL3VveVd6UmZjbkd2cnlYNkNNNkgrbXNIN09B?= =?utf-8?B?eVBjckJHUk5TRXk2bVpSYmVTU0RUNlNOZ0dwUmh5R3ZicEVqL2RXYUFNVWwv?= =?utf-8?B?cHkwSjlteGJ0MUx3eHQzUWNWNkZnQUl3SURmZ1ZOMnB5cWN2MC9LbGlyQkw3?= =?utf-8?B?YjVxUGg3M05YV2hVTzc5UGlNZHlvS3ZVdUZtY3E1VGtDbDRoeTg2R0JNKzBK?= =?utf-8?B?dG1JTUwvV2xyNEJOS256bEU0aDVIOElQQzFXSUJGWEh2bXltb0pOdVJ0NXJm?= =?utf-8?B?UFdoWHYwMTRGdFBrYW5CV09JSlQ1bUcvT1BidW5RQVkzZmJGY1NEa1ZWUXd6?= =?utf-8?B?YzBaeHcxUmFvOFA2T0tZNURCa1hTZjNLaUYweUl2Vlg5Z2p0NjVjLzFJSmRz?= =?utf-8?B?V25EdHdURmQvRzBFYlVZSE0zN1pRRWx6ZGt4YXNZL2hCaktkMEF2VUdndTds?= =?utf-8?B?RkVPTkdHUW9jWWlnSS9BQWl2U1RhUDc1WGNBcXgxTDBzb2JDN2hwV1lQK05J?= =?utf-8?B?dG9NVDIvRTFRSEJ4c0VBTS9McUNtSStCRllYdWtjMTFLQmxlbTQ5Y212V3g4?= =?utf-8?B?UnprN2dWNkNUVmdVMWlkSGxZUWFoUjhOYkEzYUVrbWNXaUZ0VG5XL0dBbjNW?= =?utf-8?B?anRxOUlMV3dnakFwY2JrYnI5VG9FSTZpNExnNUlzY1duMEdjTzExYUVGQzlP?= =?utf-8?B?anpUSDJ5OGpldVF3ZzE1T3hkbDkrRmx2R3hURjNFM0krQm43Q2w1QWVISHhl?= =?utf-8?B?SlhGT3RGcXVjZk1XMldMVGwyeHFNSmx0UHlqZFoxZStPWTVqV1Vzc09VbkJh?= =?utf-8?B?QktaQllQOSs3WXErb3M0YW85bXlvbFhGa2xZUWRXSkNnTW9Oc2FMWmRTVmh0?= =?utf-8?B?Z3dXK1M0NWpPM05SQ1d5RS9ZZ1NnSHZOZU5tRXNvdzZMQThvTTZneHplV1lK?= =?utf-8?B?WUUxVjh0YmNvT3orUWQ2RXNpK3FjeEFHSUdGbXN0SlErU05BTS9ibVRtVjRw?= =?utf-8?B?cmNjaUU3SEVlNHdIUStRejV2UFNqUTh4Ykx1S2l0UElRdTlxeXdkR1BHZk9G?= =?utf-8?B?S1E2aW1OU0E5bE9xV2V3ckxLdGNodDRBZ2tVUHN0QmtYSkoxMUNFM2Q0YnMy?= =?utf-8?B?Yk9JQUt5Zzd4RXZzWFRxaE40MDRmb3h4YWFZUnN6Q1J3WXdUYlY0K0NyaXRY?= =?utf-8?B?TkV3alpHWWQ0QlBJdmhVTWlmc3hxdjV3bGM3WXNHRnZod0lGbDRjbFI1Vjlz?= =?utf-8?B?MW5BMzhBZVN3RFNhWEdHek9JejFYVkg0aGs1NFFsZ3NuVkhzWStVYm5qS0o4?= =?utf-8?B?R2dGeFFaMkFyMlp2Rkt4bFJmaC83Mm9qMENaRWpPMVFJdy9zb1FWR1FKNlRM?= =?utf-8?B?YWRxRExvRE1vZXFrNG1xTUFtRlVTcHkwNElhdm1wTGIvenhwQnZIMWRuUkJZ?= =?utf-8?B?emViQnZudGZpMkdLOHZWM0RtSC8wZXBMNjExNkpiZFVlRzZVa01pZlIxNUxk?= =?utf-8?B?ZnNRM3JqREhzdjVRWFVMcUk3ZVNwT3hkWGg5MlpZWEMzOElkbjJzYkpOdkpl?= =?utf-8?B?TDBwR3pTcW5HVnc5R2RwUGpmU1BpSTBSMXoyckdYenVBbkRYK0l1b2xYVWVB?= =?utf-8?B?djZzVC9YL01zR0p1TVkvNlA5Ri8vUHIvZnZqUDFOUTh5S1ZqOXpoa3dLdXlt?= =?utf-8?B?dHJORjYyNURSMnBnZWRBVGlCOEluRUpkOW5qQVFUaVNEaVB5VFpybGNOTnFJ?= =?utf-8?B?azZCeFVSSzNvbVlXVUJkendnOFh3QXQrd3N3ZThtQUQ3UHZpSEVlMEhWcnVN?= =?utf-8?B?dFg3Tm50a2szWm9VbGFKcjZLVHpRNnplZUVBaDVhcGpkYnJxb2FOQWNiYnBC?= =?utf-8?B?aGNFdE9ZRjAwZFo5bXdVV25Gam9QN0lsSnRGUmt6U2s1VDIvSndadUozeW9i?= =?utf-8?B?WjQrWFp1SGUrR2pvSWdNZy9SL2xydXRzTGNEM2V1VTUyU29CYS8vcXlHVEFj?= =?utf-8?B?aVpPNmt6dHQvRG5JQXFZMGxMcVp2T2lnbGtSWWxlMXFxcVNCNVRxU2tJSWEx?= =?utf-8?B?MnhIaW83Nmx3L0g2SnptcS9NalBpVXpLUzRGdEJjYU1lanhGSEpSQWdXTGQv?= =?utf-8?Q?oDdQ=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(82310400026)(1800799024)(32650700017)(36860700013)(7416014)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Oct 2025 04:19:49.5316 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: bc0b51fb-b5c5-4244-1e68-08de176b910e X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF000044A3.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4201 Hello Tim, On 10/30/2025 2:39 AM, Tim Chen wrote: >>> I suppose you are suggesting that the threshold for stopping task detachment >>> should be higher. With the above can_migrate_llc() check, I suppose we have >>> raised the threshold for stopping "task detachment"? >> >> Say the LLC is under heavy load and we only have overloaded groups. >> can_migrate_llc() would return "mig_unrestricted" since >> fits_llc_capacity() would return false. >> >> Since we are under "migrate_load", sched_balance_find_src_rq() has >> returned the CPU with the highest load which could very well be the >> CPU with with a large number of preferred LLC tasks. >> >> sched_cache_enabled() is still true and when detach_tasks() reaches >> one of these preferred llc tasks (which comes at the very end of the >> tasks list),  >> we break out even if env->imbalance > 0 leaving > > Yes, but at least one task has been removed to even the load (making forward progress) and > the remaining tasks all wish to stay in the current LLC and will > preferred not to be moved. My thought was to not even all the load out > in one shot and pull more tasks out of their preferred LLC. > If the imbalance still remain, we'll come to that in the next load balance. In that case, can we spoof a LBF_ALL_PINNED for the case where we start hitting preferred task. That way, the main lb loop will goto redo and try to find another busy CPU to pull tasks from. > > Pulling tasks more slowly when we come to tasks that preferred to stay (if possible) > would also help to prevent tasks bouncing between LLC. > > Tim > -- Thanks and Regards, Prateek