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client-ip=165.204.84.17; helo=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by SJ5PEPF000001CE.mail.protection.outlook.com (10.167.242.38) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.25.13 via Frontend Transport; Tue, 12 May 2026 05:37:25 +0000 Received: from satlexmb07.amd.com (10.181.42.216) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.41; Tue, 12 May 2026 00:37:24 -0500 Received: from [10.136.36.106] (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server id 15.2.2562.41 via Frontend Transport; Tue, 12 May 2026 00:37:15 -0500 Message-ID: <8c4d8466-eefc-45a8-a93c-bb66d5e9db83@amd.com> Date: Tue, 12 May 2026 11:07:13 +0530 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 08/10] sched/fair: Add newidle balance to pick_task_fair() To: Peter Zijlstra , CC: , , , , , , , , , , , , , , , References: <20260511113104.563854162@infradead.org> <20260511120627.944705718@infradead.org> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20260511120627.944705718@infradead.org> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: pcRfXcGwSfTnr3S9h0S5wDF8siTlXttjJpIiN8bjNY2vonK83cXBq3bDq7lzPvnjYVd/ugN+1+RwreyhUCbKVPX1QBcYk1KyO3L56HTLcc+DGAba34WQ8oSMfJ0hLbcouTweS8PowBHpTbpbaSlfVsnr9X1M3ifxvbCqgG4DRJiWgfSqIPIjRriEXbAb7LzfS6VG4XhKd3Z6ZpLp6jT8ssKftnxQrnFN0MDPHIVlcY+iVtJUPWXpKFZBZYqEtKb+Bcd7jdN4c1o57qtXsJqdvM+n8ICTBrzfSE2PydNdDZC+5z5dhCHsGCOjM7uIzMXeTPdEHUUAx56X7plwguRJyYSbstANnWEOXnzCtcNqvq9eXAuPpMOxRaDRkz0xOipNKtDmoCMrFm5Wlz6tSCGCFBHAhYQGVgBea7UXWd8xJkGd4vDK5Lr1GNEb9x87EhaZ X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 May 2026 05:37:25.4277 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 5d78127a-8440-4d65-d4f7-08deafe88c58 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: SJ5PEPF000001CE.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6112 Hello Peter, On 5/11/2026 5:01 PM, Peter Zijlstra wrote: > @@ -9245,6 +9247,14 @@ static struct task_struct *pick_task_fai > if (unlikely(throttled)) > task_throttle_setup_work(p); > return p; > + > +idle: > + new_tasks = sched_balance_newidle(rq, rf); > + if (new_tasks < 0) > + return RETRY_TASK; > + if (new_tasks > 0) > + goto again; > + return NULL; > } For core scheduling will now trigger a newidle balance during the pick when core_cookie is reset to 0 which can cause tasks to migrate only for them to find they cannot run on the CPU since core-wide selection leads to a cookie mismatch and it is kept hanging there. Can we return early if sched_core_enabled() here or are the additional newidle balance okay? -- Thanks and Regards, Prateek