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Shenoy" , "Ingo Molnar" , Peter Zijlstra , Juri Lelli , Vincent Guittot , References: <20260120113246.27987-1-kprateek.nayak@amd.com> <20260120113246.27987-9-kprateek.nayak@amd.com> <3017c721-e4cc-4c6a-b2fc-51e2c8e01711@linux.ibm.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <3017c721-e4cc-4c6a-b2fc-51e2c8e01711@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWH0EPF000A6734:EE_|CY8PR12MB8339:EE_ X-MS-Office365-Filtering-Correlation-Id: cb3e5393-2c85-4db8-4a0d-08de5a488115 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|82310400026|7416014|376014|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?S0xpZ3V0c09GWTNPSmdpY1FRY3ZKaHQ2eTFHa3BOSzlIRnhHUVk0VHZYUmNh?= =?utf-8?B?MGlBT1JvaithV1A5K3ZHS3IxblIwSUdMMmhFYUZwdVJ2Wi9pSXMzalA4bkZ1?= =?utf-8?B?TCtxMWJuMjBHY1JGakFiSGc3ZEp2Y051WEJ5YjQwUk9CTUVjdU9HWXlFei9w?= =?utf-8?B?Z3NleEpobThvNVI3MktjSFlHbDFkVzY1a3pvMmRJSWV2citLT1hHWE5zdktm?= =?utf-8?B?cnpLMzhVYXg3eTV0VmhNTzB4YThkMHoyeU1GcTErdDBUZ1hCQ2VNOHJ2aEpG?= =?utf-8?B?VjQ3OHRsS0VoeWttR0JzcURHOXJXcWI3ZkNPbjhqUEFnUG8xS00zaWxSZ0xr?= =?utf-8?B?aWZOMzRhNml0RGlFNEdtWHVNK1JzdE5BKzdISU10UWJVZ0hEeC9McXlBai9j?= =?utf-8?B?L25JMkJBVENxUi9JWDczZVRhdHdIUEg2NlJNRm5nUmowVnNqVWM4cWNhWk95?= =?utf-8?B?Z0kvSmJ0RnJQQU16NXE4RjdCOFJHaHVkaDI1OGFCRDhld1c1UitNdHVjQnpW?= =?utf-8?B?aEl1ekJKYTBzUTNLS2ZUQ3JGYnhOZG5SSTVCNTZzMmxVdVZiMFJnbWlLaito?= =?utf-8?B?WTlMRExNdUV1RXhLTXJ1dEhTZktXMGhEV2xmT3JkTEdMWmRHK1ZTR09aYXRM?= =?utf-8?B?OFFNY2taL0RaeVNwN3VnUDI1dDJMWlhzNG0vSDRWQ2N5Nnc0SDZiMkI0NUs4?= =?utf-8?B?Mzc2M2M3WDI2cUdlYU5DQWpHNXlBNE5Fa2hXUzF3YXBtOEFrRXJxSmh2SHFW?= =?utf-8?B?TmhGTGtNSGpmdVBMK0FGNjEzNzVPd0dwcVZObk9QNGhoczVkZGhPQ0xXQjB3?= =?utf-8?B?dDU2VEx0UlJWVHlLMXhSZ2tsOEpXWVJHaU9kTCtkZXZGa2xIMm9QY0Z1UUNn?= =?utf-8?B?L2hRdHh1a1AyWkFXYWJGZ0YxZVJ5OVEwVTFwd0hIVjFZbFpDQXNud1BscU4y?= =?utf-8?B?N2VwWFF2bW9qY0VSWXhOcG9Eem1xWUxwaTRRLzBZU1pSZzNsMnlJUDd4MFZ5?= =?utf-8?B?eGlyQVNTK0s5cVArUENDNE1kaFltOVJkWmNRM0tLVDZsVGVKWC91WExWZ29h?= =?utf-8?B?QXRvd3E4WnhQekUraXQxRFlLT3FvTkQyejA1Y1BkeG94MkhpaVRxNE5ERDF2?= =?utf-8?B?VE13RzZrOHNGNlJFUC9GL0cvYW1KcGlMZXVJRWlTTStHZFRaOGh4S1FRL2tz?= =?utf-8?B?WUJaQ0kzSENHWGh5eHQ4ZlpFRUVvWGFsOUpEQXNLbTdnWW16b25ZSDBBS2Fn?= =?utf-8?B?NTV5UjU3cmhwbVlHZnpJbEo4TkZZRDBnN3Z1U0hyeDNzRE8wRXlLcTcxd1VZ?= =?utf-8?B?QlhMWjY1Z2ZSZ1NGRkp5VklZOG9Pa3MyY1ZES1FpblRhek9zT0dPL1E4WFF1?= =?utf-8?B?MFJvMng4cDhlRmFocHpKZThucHR4czA0TFFaYzQ0VHBqTjBpQmh1R09SRGFk?= =?utf-8?B?NEJXUG9weEljNzByU0ZiOStpY0tFdE9pcXhVTTF5UFlwZlJueGNIcTZ5T3Bh?= =?utf-8?B?ZkdmVzB6U0ZxZDg3YmZpcVVyRVpkR1NEQXlkV3VxR25LajVqdkdNZWlEYTFP?= =?utf-8?B?eGVZNXNVcXRHOVplZmJsVzQ5QWp5Y1pnZ0g5NHVIdlBjeVpIVjVHVUEwaEJo?= =?utf-8?B?dTJ4ZVlTRjBsNmxkT1F1eWJTSmxGUmFUQ1BPWndySHF1LzVZeW9TWFpUTzlu?= =?utf-8?B?UjNhRDNRRDk3L3RuR0lEMnVFdnIxdktuUnVYdWJrS1dsVTFkNlMybjZVdXV1?= =?utf-8?B?RXYzSzBFM21VUGxlUHVQUkFvTTlROWdLZFZVS3N4WnFGbHg0ZHdPNlF5a05D?= =?utf-8?B?WEx6L0Z2MEg4TklDVVoydmYvR01zS3RoU29nYzNTVXdpNHdZVS9paUZiL2pP?= =?utf-8?B?eVhCb3V2ZjczY0ZIUWlwK09vZHJSR2dEcDBucmlMSXI5R3lMbEtpZ01JNklv?= =?utf-8?B?Qmo2VWZPRm4rdnJpa3NOQld3M3NtbWNGOGtlY1JPdkQ5UUlMYUwzNnRMQXkv?= =?utf-8?B?UGRWWlExdXpvdDFxeFh6WHhHWFJWcVJ4aG4wQnpRR2IybWQwVUhWdTRHcE9h?= =?utf-8?B?d2VPaUgzQlNXS1FkbkRncVdOck9QRkU4d3JUNHlWNjg2cHRNTW9EeCthcWhY?= =?utf-8?B?akFndERnaGpQS2tCSjk5d3RtWTQxQXowNVZXOXVtR1F0SWZsdURrMEVoM0pV?= =?utf-8?B?MlhSeEJuNlpibmNZdDUrYWMrT0xhUXZNbXQrZkp5d3A5UzR3MFcxWWtZTkMr?= =?utf-8?B?U0xTVWlXYU9wZ0ZNeTZoVGNQNTN3PT0=?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb08.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(36860700013)(82310400026)(7416014)(376014)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jan 2026 06:27:38.1649 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: cb3e5393-2c85-4db8-4a0d-08de5a488115 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=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: MWH0EPF000A6734.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB8339 Hello Shrikanth, On 1/23/2026 11:36 AM, Shrikanth Hegde wrote: >> +        /* because !--nr is the condition to stop scan */ >> +        nr = READ_ONCE(sd->shared->nr_idle_scan) + 1; >> +        /* overloaded LLC is unlikely to have idle cpu/core */ >> +        if (nr == 1) >> +            return -1; >>       } > > > I stared at sd->shared->nr_idle_scan for a while to see why it is safe > even when lets say there is no LLC domain. > > It is because it is sd_llc here. Not any other domains. and > there is sd_llc check before calling select_idle_cpu. Ack! We come here with a valid "sd_llc" from select_idle_sibling() and "sd" and "sd->shared" are freed at the same time via call_rcu() when the last reference is dropped so having a reference to "sd" guarantees "sd->shared" is not freed and the topology bits will ensure "sd_llc->shared" is always present (or it screams and we crash here). > > So maybe add a comment here, saying null check for sd_llc is already there > and that's why it is safe to call it directly. > >>   +    if (!cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr)) >> +        return -1; >> + >>       if (static_branch_unlikely(&sched_cluster_active)) { >>           struct sched_group *sg = sd->groups; >>   > > While reading this series, this reminded me we had discussed about unifying > sd_llc->shared and sd_llc_shared thing into one (in v1 or v2). > is that dropped or you plan to fix it after this series? Must have slipped out of my mind! I believe the only other user of "sd_llc_shared" directly would then be nohz_balancer_kick() and {test,set}_idle_cores(). Out of those, I would only consider set_idle_core() from wakeup to be a fast-path but we'll already have a "sd_llc" reference there so we should be able to flip the idle_cores indicator without needing an extra dereference. We can only keep per-CPU "sd_llc" and remove "sd_llc_shared". I hope that is what you were suggesting. Otherwise please let me know if I misinterpreted the question. > > > Other than minor comments and nits series looks good to me. > So, for the series. > > Reviewed-by: Shrikanth Hegde Thank you for reviewing the series. -- Thanks and Regards, Prateek