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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by MN1PEPF0000ECD8.mail.protection.outlook.com (10.167.242.137) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8655.12 via Frontend Transport; Mon, 21 Apr 2025 08:54:38 +0000 Received: from [10.136.43.233] (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Mon, 21 Apr 2025 03:54:34 -0500 Message-ID: Date: Mon, 21 Apr 2025 14:24:26 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 3/5] sched/fair: Update overloaded mask in presence of pushable task To: Shrikanth Hegde CC: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , , "Dietmar Eggemann" , Steven Rostedt , Ben Segall , Mel Gorman , "Valentin Schneider" , "Gautham R. Shenoy" , Swapnil Sapkal References: <20250409111539.23791-1-kprateek.nayak@amd.com> <20250409111539.23791-4-kprateek.nayak@amd.com> <2dae733a-689c-4574-a4dc-f59f11fb0893@linux.ibm.com> <616187d5-e178-4fa5-a0a2-1509f11d1a37@amd.com> <97aaf3e5-22d7-4020-964c-891ad619bf4f@linux.ibm.com> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <97aaf3e5-22d7-4020-964c-891ad619bf4f@linux.ibm.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN1PEPF0000ECD8:EE_|MW4PR12MB7016:EE_ X-MS-Office365-Filtering-Correlation-Id: 6d794319-2959-4a13-65db-08dd80b2262c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700013|82310400026|7416014|376014; X-Microsoft-Antispam-Message-Info: =?utf-8?B?UGI1TmdMdUd2eTEreWNmU0E0bnVjdDk3TmtJK253bFpFeUM5b1JTVDRpOG40?= =?utf-8?B?SVd1Qk1Tay9UY1JDOFZ6OWxIUzdOajBIc0tzSG1zWVl1YklDMjExTVdERjVy?= =?utf-8?B?T0JzVzVUT3hGOWVvbnRRTS9Rd20vbHQyK2N3WS9Tdk9vU3MrcEc5R005N1Ni?= =?utf-8?B?V0Z5Slp0emZaQTJkalFYbWVFSWlsQ0theGxvVCs2UGJ6ckFYVUZPUXNhQThL?= =?utf-8?B?akxQZDVXUTRkZ1NNSDdIZWNrMFBrNGlmcHh1SFhWZnltWUdRWVBVQU55Y1dy?= =?utf-8?B?QTFBbWRJTExNRjZteXpCMzcyUWV3Rko0RXlmY0tnc3pqOHFFbFBxY21QQkgr?= =?utf-8?B?bzhCZm9ZR2tia3A5QVdySnZQR0RzRko0YWNvcW95WUw4UXJURldCcnA4Ty8x?= =?utf-8?B?TDZlWEIrWFJ1SVlzMXRzU3JOZy9tRHhTRTgvSm9yRnE4YXpjbGpjSHJhdHVn?= =?utf-8?B?QTJpOTdBZzM4bXFRMVFuNWUvaGlNNEVwazhTY3BJckdqdlJhZGMva2MzU09p?= =?utf-8?B?WWRRTy84dUF3NjYvNmNxbkFTN3FtNlkzbnZYVDJyY0VxSjZTa1VDenFlQVJ3?= =?utf-8?B?L241STFNZ240cGpUT0tOYnJjVm9BSGJvcW56NkE3dzN5djVSZXRLeWJacjZt?= =?utf-8?B?T1lmRklZZEhQVkFNQlZhS01rb0F0OHFJWWFtR1d0WlNabGFMRVN3R1EzY1ZQ?= =?utf-8?B?eTB5QVVHSXgxTHJoZHFZM2tuT0s5NjNvcU5ic1dhSUc2dlU4U2N5VUZST1FP?= =?utf-8?B?cGJTODVDWDBZSDVWMTBkK0JtbDN4VWZnTlZkMVliNm1lUExIOEFBTWowZXRt?= =?utf-8?B?Uzl3TjVsSHNCSzNNa2lrS1dveXFUYjNGRWczdU4rUUFlTDhBZU9nRnBLZm5X?= =?utf-8?B?ME1ROHE4UGFMQVFGM2Z4blBVVWliYWNzRkZEb0gvaTJGZnJWc0daWEJPbVZB?= =?utf-8?B?Vjg3VDNxby9NMnRMUHZaQ2F6YkNYUldLaGVrdUJ1eFFacmVvMTlsNXhqdUJG?= =?utf-8?B?N2JPK2gyVzZSN1Fya2Y4ZmN4azZKSWJ5SG43ZHVQSyszRHlTRjM0YlVkaUhN?= =?utf-8?B?bGlPTVBDcE1vc21zNEJYckxtZWsxOERpZzZ2cXN4aEQ5Vk5Mbk4zY2RPZnBm?= =?utf-8?B?U25UK3lMT0lLc3d1UTd2QitOSkVOQ1ovdlVDRkxFMWNrOXpDbFhOSUI3aGdG?= =?utf-8?B?cGNBZ0s0Vk5ZWnp3V0o1NFErV3E3M2wzUWlLK3o2ZXU5OEtpQXlYa0lQU1ZK?= =?utf-8?B?UDIvazh3RUlveU1QbzRCTDVLUFI1RWNPZnlRSmRjV0cvZjJna3ZGTHRIVmpK?= =?utf-8?B?OXcvYlVQTkhkOVg0YlozbVg2THVCZ3A5cHcwWDc2Sy9qN0x2QldOUmNPQ1lX?= =?utf-8?B?VEQvM0xCQ0VGbTJSRTdGL1hMWkUwZ2VDelJUTkNZbHoxVXM5SmlKRDBMcEpQ?= =?utf-8?B?a2djRlIvU25YYkZXVjdFWWo5TERETmFXMENGOFVTZVgzeFlLRkV1UkdCTVc4?= =?utf-8?B?SDVQaEM4RmlmTXNqU21LOEpHSVRuSDFFOUJ2OUFjR0s5dXZWYkZwRnhvU0ZX?= =?utf-8?B?NUFwL09IZjNYeEltcnlaY2lqNDY2aW1wNXoxS0NjWVBKRjNWZ0ZLODRhdHd5?= =?utf-8?B?UXppWmVJVzJBaVRtYUVSbjR1VEFsWGpybVN2OXozdTNsSkE3Q0czSG9pMG1Y?= =?utf-8?B?THlqS1JoY04yZ04wVE1mYU5iZzBCQWpwZkpwNS8waXI4K2RBQjNyaDd5WW5Z?= =?utf-8?B?b3ErL0xHc0dSRFJncEd1YUIyZUVxM1JVNEsvdjIycmJSWm5BUkpyZzBWeGEy?= =?utf-8?B?bzVJbG1vd3hqeTg5b0J4eGFzWXVuQWlqODh1My9SSzFMcDA3TVRUVTlWdVB0?= =?utf-8?B?eUhUS0FMckNWeTFWcExxYVZhajBuM2FmekhCYjJYMEtETEhKYTczUmVBUThm?= =?utf-8?B?Z0djSVhwbUNYODdkU1lObURGSWNYTUdIWTJLR0VEaVkvK0pnb3B5ZlRGdWFM?= =?utf-8?B?cGRxZHBZWGt3VkFTYTcyM0kzclhnTE93MnFBNWV4YSsvenJCemwrMWVZd2to?= =?utf-8?Q?GSyZHu?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(36860700013)(82310400026)(7416014)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Apr 2025 08:54:38.9021 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 6d794319-2959-4a13-65db-08dd80b2262c 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=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: MN1PEPF0000ECD8.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB7016 Hello Shrikanth, On 4/21/2025 1:33 PM, Shrikanth Hegde wrote: >>> I was getting below error when compiling. Noticed that overloaded_mask is a local update and it wouldn't >>> update the actual overloaded_mask. >> >> Interesting! Question: Do you have "CONFIG_CPUMASK_OFFSTACK" enabled in >> your config? (me makes a note to test this too in the next iteration) >> Looking at the arch specific Kconfigs, there is a slight difference in >> how this is toggled on x86 vs powerpc and I'm wondering if that is why >> I haven't seen this warning in my testing. >> > > Yes, that's the reason you didn't run into. > for me, CONFIG_CPUMASK_OFFSTACK is not set. Thank you for confirming! > >>> >>> Compilation Error: >>> kernel/sched/fair.c: In function ‘update_overloaded_mask’: >>> kernel/sched/fair.c:8570:25: error: assignment to expression with array type >>>   8570 |         overloaded_mask = sd_share->overloaded_mask; >>>        |                         ^ >>> kernel/sched/fair.c:8571:13: warning: the address of ‘overloaded_mask’ will always evaluate as ‘true’ [-Waddress] >>>   8571 |         if (!overloaded_mask) >>> >>> >>> >>> Made the below change. Also you would need rcu protection for sd_share i think. > > Or you need to use like below. This also works (Not tested on x86) > > struct cpumask*  overloaded_mask; Ack! Perhaps that is the way to go. I'll take some inspiration from other cpumask usage in kernel and adjust this accordingly. Thanks a ton for testing. > >> >> You are right! Thank you for the pointers and spotting my oversight. >> Aaron too pointed some shortcomings here. I'll make sure to test >> these bits more next time (LOCKDEP, hotplug, and >> !CONFIG_CPUMASK_OFFSTACK) -- Thanks and Regards, Prateek