From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from CH5PR02CU005.outbound.protection.outlook.com (mail-northcentralusazon11012061.outbound.protection.outlook.com [40.107.200.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E00718821 for ; Fri, 26 Dec 2025 03:17:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.200.61 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766719044; cv=fail; b=hIE747zLSU0WYK1lqLv9V6qA3pMnaqEPk3bodEuQI1f6jJOiu0kRrB6WRDqGZo4AstLDJ0wM7aBq9Tu4ZeHAaWzk5tn6urzjPe146xIWVA7iBEGWD0BLlu0ROKBm2hM8PH5Mxl8I0XBWYChEpE428BdBliGDYt6wwz4YLpJspOU= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766719044; c=relaxed/simple; bh=3RshlsuwfkmnRqJodOYdyRd4xp22XXOBpWEY9i1XF/Y=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=igP67CtgZzBkfSlzgk+Avn9pohnCKG43kgm2OcdJ0oFWi1bLV/WVxIxgzPQgmZtKslGQ+cAznbgcO4ZZe7FeGSNKRLQeywDPeGtmRntwDGG9l/HN8r18z9gFgRukxD0dXOnVlrAsAzCuPA2uLOrXBGOpUzZX+leuzF6istZVMUY= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=jjQZEAHM; arc=fail smtp.client-ip=40.107.200.61 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="jjQZEAHM" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=YgYw2VIq/mLuHytGMAbXJhCy8dpX6UVVIZXOXoN9cGI6kPCh6VXGfL7mu3keH+gLlEnpM+Exr0OevCKRyCQTx3YYX0TiOTzfXW3G0xw2Q44B4imn4zJYYtKUqHE1/Pa9kFpljgVdOPhSXYrk6BIJxxlpQ3tssHTr+pcKTegRmuea4DY8yR926fSsLNigP6R0Bm66M5h5JbJfCkJibJBcu/4/HuyfdWGIygu9vde5/w7kN5AO6UwdiqfgnqJr22nqZ0luDY6+hO0Eq0g+jj6EQA1FMY4ZVePpEcZFbPqGmvH6YpoYmRd28KBR2ZXOMTmgd0KYCsfGrr7QQ6GkW0FF/Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=NplQLLOf5stK6SSFreqIcoMn3LUVqAAuQMXV9aA12Z0=; b=rroJHWoXwDd8tAytEam212tTPNOEVhQmZUdx3MzPjSuXzNbmq5LouQzB3FpC7F9KggB0uDbWEqZaYeBlU3jFj6aUU3aeE1clE1/1Dl/AAlPCAA0tMRUJSxRxvWhw2/7BL80o0t8U3DaoiJK2UGtixQr26wFw0KxrK891xnn5N/lSlCRB6kvvnWP561zlCVpEyVpav6VlVBLVJj5GXtC7L/8fIcnN9Y6JPgEVMjIBdXrhsmJUpdlMyspxMPMBZcVuB2WwdkV4W4W3exFX/v7sQEBBJy3Iky+E0VxGUfR4hU6xfHq2QLEkg9h/AMemnm4VVJqUGJcz66ORFLERvyQcHQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 165.204.84.17) smtp.rcpttodomain=intel.com smtp.mailfrom=amd.com; dmarc=pass (p=quarantine sp=quarantine pct=100) action=none header.from=amd.com; dkim=none (message not signed); arc=none (0) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=NplQLLOf5stK6SSFreqIcoMn3LUVqAAuQMXV9aA12Z0=; b=jjQZEAHM+to5zdtjMttFEdh5RkOkNIQeFPTXIs1Wz4b7mHc96adZE2Vx1g1imKGQYTj3/Kat5sfwSjynvs0L7SMvmKwgwQyweC8nnUfRM0ovV8qHfcIapJjFE9DYf+ILZGowSDv83OTxL3d6Ftbmy55PdoAsW8R8e8cIg5lpErk= Received: from BL1PR13CA0445.namprd13.prod.outlook.com (2603:10b6:208:2c3::30) by DM6PR12MB4356.namprd12.prod.outlook.com (2603:10b6:5:2aa::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9456.11; Fri, 26 Dec 2025 03:17:18 +0000 Received: from BL6PEPF0001AB75.namprd02.prod.outlook.com (2603:10b6:208:2c3:cafe::90) by BL1PR13CA0445.outlook.office365.com (2603:10b6:208:2c3::30) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.20.9478.3 via Frontend Transport; Fri, 26 Dec 2025 03:17:13 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 165.204.84.17) smtp.mailfrom=amd.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=amd.com; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by BL6PEPF0001AB75.mail.protection.outlook.com (10.167.242.168) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9456.9 via Frontend Transport; Fri, 26 Dec 2025 03:17:18 +0000 Received: from Satlexmb09.amd.com (10.181.42.218) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Thu, 25 Dec 2025 21:17:18 -0600 Received: from satlexmb08.amd.com (10.181.42.217) by satlexmb09.amd.com (10.181.42.218) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.17; Thu, 25 Dec 2025 19:17:17 -0800 Received: from [10.136.32.17] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.17 via Frontend Transport; Thu, 25 Dec 2025 21:17:11 -0600 Message-ID: Date: Fri, 26 Dec 2025 08:47:05 +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: [PATCH v2 04/23] sched/cache: Make LLC id continuous To: "Chen, Yu C" CC: Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Madadi Vineeth Reddy , "Hillf Danton" , Shrikanth Hegde , Jianyong Wu , Yangyu Chen , Tingyin Duan , Vern Hao , "Vern Hao" , Len Brown , Aubrey Li , Zhao Liu , Chen Yu , Ingo Molnar , Adam Li , Aaron Lu , Tim Chen , , Vincent Guittot , Peter Zijlstra , "Gautham R . Shenoy" , Tim Chen References: <2f9165fe-55f2-4919-be01-e9d2cdd1f960@amd.com> <70ac9110-d899-4a74-bd3f-54a486a7e45d@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: BL6PEPF0001AB75:EE_|DM6PR12MB4356:EE_ X-MS-Office365-Filtering-Correlation-Id: c5522289-cff5-4f8c-c5d0-08de442d46be X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|32650700017|7416014|376014|36860700013|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?aXVuYzVISHB0K3hkUXhXWFNNM3pwNnpVNzhJT0dnMThOcWVNZUlaeWZ5ckpi?= =?utf-8?B?NDJKdDN0aFNicHVGUHlhMDR2QU9IeGkrN1M4M0JHanY4Y3BwbHk4dGFkSDZL?= =?utf-8?B?Slhick9JOEVBelRJR3RyTUdlL2lGZXFzTk5XYVNNWitWQjlUVExEcDJqV3JT?= =?utf-8?B?WnpEWTI1UnYxakF6QkxtUzNENmcyeUhPR2lQSEJCMmttWEdOWE0wSUxaamZm?= =?utf-8?B?eks5ak5uc1NseEJySU9FOTNaY2Y1dGltUnNUQnV1Tlh1engzSnc0YnA2SVB4?= =?utf-8?B?L2t6SC9kRTFUbmdOK0lsZmZPOVFzb3phNllzbE5QNVFlQWg5TklpbHZUZC8w?= =?utf-8?B?bnptOWhleEViUC9yMFVmWnN4UWVEMUhQZ2lWQWk0aktVQ3N4MWVXc1VSVEMv?= =?utf-8?B?MWpaYXcwNnZvSWcxRDVMbVNDTDYwaWFDemFNejhseGhTT2lKMjVWaVhvcHpO?= =?utf-8?B?Q3lGYlBienhkbkQxc1pwbFBXQXZYb1BJdFoyY05mMUdVODJiN09TRHBnU2ov?= =?utf-8?B?OUZrQytENzg5QjlVVGpFOU9QcVpDckxQM3hJUnVNQU9VaWl1RkpxSktzT1JN?= =?utf-8?B?ekVvUm1JYytJL0txanVDdHU2VmkvcEV1NUdiUlRUOXVPNHh3aWIyTHlvUVg3?= =?utf-8?B?UlpVSlRkMTU5U1NjNlpQQjJGMEdGak5oWXM3alRhSHFOTjAvVlVWaU40WEFr?= =?utf-8?B?cEp5VkdHTTRVVWNLTmpjSlFuZGYvdCtWNWJnR1VoNmt3TTR0Wi95cmRzMlMv?= =?utf-8?B?M1ZFKytpVXZSbERCQTNhVG1PR2ovOGpXdmlmRUpKRmRocGlJVXFnUnJPa2Vn?= =?utf-8?B?UjFQTSttc1VYMzd2cHNabHFUZ25vR0JiY09Zb1hJUnVzOExLQlBNZXhPYVNw?= =?utf-8?B?Zzh2YzQyczlEVTlvaDZiWFlmTWFLSDF0OHUvcHJhZXlTODVUK2k2cVpiQkUw?= =?utf-8?B?Zms4WDU4dzNNanRDNjZUOVR0TTJDU2xPUjdjMkczbzFKai80WW5MOHc0a2Yw?= =?utf-8?B?U2Y5MFFIcUV2c09ET3ZPVXV4Vk11SGM1NWpMS0h6RndLV1lEQUZWQmoxVmhI?= =?utf-8?B?N2NvSlVsL09Gd1ZqYTI1ZFFCbmd0ZUZJNFRDanNQcjJaK3U0WE9CMUprdkNs?= =?utf-8?B?WlRhb3VieGgvSGRsU25lQ3pJTDNmS2x2SitIbU1xWlhoTTFYbDhMdzlKYkh2?= =?utf-8?B?U25DNFdodlYwbDg3YjFCYjZyUDhHSXQxVlZOY1Y3d2ZPbGRHbFlmdk9mOFMw?= =?utf-8?B?eWN5cGVZT3FqYVF5TDd1WFpLZkJUMDBKMVQ5RWI1b1UzQmtBR2lCMzhHSFJx?= =?utf-8?B?bk9PdEFkMk9YdVUwNmVzYjdpL04rY1k0L1N4OGo5OGozSWRadEhidW93SFAr?= =?utf-8?B?akdwYWtDVHI4aFlieU95YWYyQ01mQ29ic3hOTzJ6M0J6K3dpRDRYcG02dUMr?= =?utf-8?B?UFhBQzJ6elpGc3ZvQndDLzd2OGtVaE5sN2VxdWxHN1QwMko4bmU3VkdXLzgx?= =?utf-8?B?ME44SGIrQmVBUzdnTVVYREtGNS9WNVVnbmpNaGpHZytPekRMUmVNcHFUVHhm?= =?utf-8?B?QUFmYWZCaSsyWUdxTW5CQmJaVERuSkFIZmNsNnVzV2FmbnEvMkE3TGZmZ2xx?= =?utf-8?B?T0I0MGhUdDFMU2l0TVVGbXF3VWRTNDdXSTlSRWt6a20wTHhjTTkrNXQ2VEla?= =?utf-8?B?b1EzcDdVZU91VEFjd2tXaXJCUHZ5TUlsMklLY1Ftam45UG5vQ2xYdjAwcmlH?= =?utf-8?B?c1pTOS9CU1JRNC83a3VzV0hud3kxS1ExeWphZmJCQkkvd2ozbDVnYm1QSFlw?= =?utf-8?B?RjNady9DMTRHZXQ5dnF0azhXTktsdzlCQUVLaTdNZGZ1eVJzU2ZJTjJNWXY1?= =?utf-8?B?eC91RFhjMzFRcHpQM01pSjhWSjJHditXWW1VRmlSMDRZOFY0cllkak1DMWhQ?= =?utf-8?B?dmhvS0hTcVdEWnRGbVpQRklRZVd3ZTlaMEZieFYrN1FjeEFDVXJFNUdwR1V0?= =?utf-8?B?RG5QeUlLOS9IcG9aNzJEcmJWZjZscitNSTFkTVRzNUs5cnA2OVdzbExkbCtI?= =?utf-8?B?MnVTVG5mVzUraVZTM2pva0c2cnhnQXlyZ0h0NHVJUWdGZVQwNHdpZUo0cFRq?= =?utf-8?Q?5WnM=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(82310400026)(32650700017)(7416014)(376014)(36860700013)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Dec 2025 03:17:18.3876 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c5522289-cff5-4f8c-c5d0-08de442d46be 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: BL6PEPF0001AB75.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4356 Hello Chenyu, On 12/24/2025 3:16 PM, Chen, Yu C wrote: >> Only case I can think of is a task wakes up after partitioning >> and it's wake cpu from a different partition is mistaken to >> share the LLC as the current CPU - but the task cannot actually >> run on that old CPU and it'll have to take the >> select_fallback_rq() path if prev_cpu was selected during >> wake_affine(). >> > > OK, make sense. > Actually, prev_cpu might not be chosen by select_task_rq_fair()-> > select_idle_sibling(), because fast path select_idle_sibling() >  is expected to be triggered when prev_cpu and the current cpu are in the > same domain in select_task_rq_fair(): > cpumask_test_cpu(prev_cpu, sched_domain_span(tmp)) >     sd = NULL; //wake affine Then again, there are cases where want_affine is false, and "new_cpu" is initialized to the prev_cpu and we continue down to select_idle_sibling() since "tmp->flags & sd_flag" is always false - WF_TTWU matches with SD_BALANCE_WAKE but no domain sets it anymore afaict. Again, going through the fallback selection path should be rare (once after partition on wakeup) and shouldn't cause any problems for most real-world scenarios. > curr cpu and prev_cpu are in different partitions, they > are not in the same domains. > >> I don't think it will be such a common occurence to cause an >> issue and even without that wake_affine() could still the >> prev_cpu if current CPU is busy or via wake_affine_weight(). >> > > I realized that sched_cache has added cpus_share_cache() in > several places, most of which should be related to load > balancing, which should not be a problem if llc_id is shared > among partitions. I'll double check. Thank you! -- Happy Holidays! Thanks and Regards, Prateek