From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.10]) (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 C1F8420C48A for ; Wed, 10 Dec 2025 23:58:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=198.175.65.10 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765411111; cv=fail; b=HM7oQkEQlIh3JoG88LsuaLPh2oHhX2HJLRxSEG2pze1Or2gITFpoNNXtb+B3XrzI/UKhDRlzoCUayOnD8qZ0CedFoGSyMm8jQgIJmJYNo1bN2eNv5xwHAbZQ4nEbQaVRYxwCEu2TADrzXfLwcXXI3PM6SL4LAxArOCyQClFoQ7g= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765411111; c=relaxed/simple; bh=rYDLr5vU+QIgG2xHnWGqqYfxrEFFu2sJMtui1cjrQQA=; h=Message-ID:Date:Subject:To:CC:References:From:In-Reply-To: Content-Type:MIME-Version; b=Fx4OXvji2EvJkiu9uXY5HagsuJz9j6QD2Jarppru+bqf7YwZAJZ1dtBmqUgSanx5LXn4D00rLfAq4B4NizDQqZd49BgG6dhUojO7WxdQQyLq5W406IPVM8I/JQPKJB3vqr5UEJ6pihHTbLGCOnQQmYf959BZCguhsaUAwNNrIYI= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=ArJNxSlr; arc=fail smtp.client-ip=198.175.65.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="ArJNxSlr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1765411109; x=1796947109; h=message-id:date:subject:to:cc:references:from: in-reply-to:content-transfer-encoding:mime-version; bh=rYDLr5vU+QIgG2xHnWGqqYfxrEFFu2sJMtui1cjrQQA=; b=ArJNxSlraFHJDdei1ND8aY8PEwLySZzdVrrSHEcbAl/tp322wr+DSLnh 4hGdcx+Nhd2NORLFHqL7WMRxc6emD9zw9XKsGdMs+Ns4Ghx3r7NBHXIEg N2TVDutY179TzaR1nYZrUURPBrZT05iQcm0lCiZo1bO6blytVgii41EGP oqxZXfQgliCWWhHb/RKxY+QwlPKmWKmE6mai3cdE3sj5GAiutbwj6P5Ug Dm77AQ+lWzQDgtPs2hxs0qYj9OTONjUCPGyFB5Mv4pRKgVbecePHvnyq/ n1Ka2V+gnt0biHgXHi/zz+lHgSGi72/Kkd5Ax9FIv7aaBoclSlljgm8PW g==; X-CSE-ConnectionGUID: b/yfrISUQTq0E9R78Q9bAQ== X-CSE-MsgGUID: 4QSGx8gIRsmoa46bScwdWQ== X-IronPort-AV: E=McAfee;i="6800,10657,11638"; a="84798533" X-IronPort-AV: E=Sophos;i="6.20,265,1758610800"; d="scan'208";a="84798533" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Dec 2025 15:58:29 -0800 X-CSE-ConnectionGUID: BFsEiURsRWmz/cx3KEwlGA== X-CSE-MsgGUID: Bb6D4YwbRvidN+PYD74LIw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.20,265,1758610800"; d="scan'208";a="196541205" Received: from fmsmsx903.amr.corp.intel.com ([10.18.126.92]) by fmviesa006.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Dec 2025 15:58:28 -0800 Received: from FMSMSX903.amr.corp.intel.com (10.18.126.92) by fmsmsx903.amr.corp.intel.com (10.18.126.92) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.29; Wed, 10 Dec 2025 15:58:28 -0800 Received: from fmsedg901.ED.cps.intel.com (10.1.192.143) by FMSMSX903.amr.corp.intel.com (10.18.126.92) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.29 via Frontend Transport; Wed, 10 Dec 2025 15:58:28 -0800 Received: from PH8PR06CU001.outbound.protection.outlook.com (40.107.209.32) by edgegateway.intel.com (192.55.55.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.29; Wed, 10 Dec 2025 15:58:28 -0800 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=TfGvODNKyVI0sibLFBm431191RjO4ZWPhgXOMAamL9hHSNYbs7Tp0BTMLG4+AHETYF/5oPvNDkqufDzCVdf4GHsQMH8Es7Fso03gMQVw2se9kcc1xH36WlkFvvlII7IFsIDN3kDUxTRo6DfeGZsZRkj5bF/moKiAw7/+jqRcVsQu0M0meI3INOd4d/sXyvlwdzVHVQdpj3R+X72liR5T3t5u+BE5nqRnC2dAnk0RqCkuDXrUV1A1yeAdwGV6XfRU+Rq8t66XdZNXM+UtRVtgDtrraQqP1zrL/giNTpKqYyJaTJ2XBBwgecONSGv1PkIsrrsOHIBGmoO2ulE4b1UHyA== 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=Hxepv7hw2EtpG4c0FdymcCZxah+rY6H6+Xj1+SrYOmU=; b=GBIp0/WZKr/CSLe/Eo/xOKCduCxa4+9KkkG9Vr29U6ZswJ+bdbmBlBMSqv5CJ4qO0ckXYPeg8le+PTzkSr/c7NiugG5Q9UVuPUhMv1+FipAEP8nNs1sHn0Bu6djPfJjDlE4HuDP87KaZRTp7Fvp7i1bkOHsVQVyH+dHlsm+G4nm332v4nZ3HT+b3tQX59kaHpY2ivRkdNc9uEBM0Rgk/V4XapilyI553O+KTpNIPzjGXY0u6k9TYPcG2sjINWUJMv1SrikUYj8y0y8Gb6GdUYrv4PC6M0IwnlaxDqBoXl09A1vWBQmo/JuNa+Jw8ceRSG5WEnzTBoTrF2l4tXqR2nA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=intel.com; dmarc=pass action=none header.from=intel.com; dkim=pass header.d=intel.com; arc=none Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=intel.com; Received: from DM4PR11MB6020.namprd11.prod.outlook.com (2603:10b6:8:61::19) by CH3PR11MB8443.namprd11.prod.outlook.com (2603:10b6:610:1bd::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9412.8; Wed, 10 Dec 2025 23:58:21 +0000 Received: from DM4PR11MB6020.namprd11.prod.outlook.com ([fe80::4af6:d44e:b6b0:fdce]) by DM4PR11MB6020.namprd11.prod.outlook.com ([fe80::4af6:d44e:b6b0:fdce%4]) with mapi id 15.20.9412.005; Wed, 10 Dec 2025 23:58:21 +0000 Message-ID: <30941dd6-52cd-41f5-ae9c-3966cf7a6653@intel.com> Date: Thu, 11 Dec 2025 08:58:12 +0900 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 02/23] sched/cache: Record per-LLC utilization to guide cache-aware scheduling decisions To: Peter Zijlstra CC: Tim Chen , Ingo Molnar , "K Prateek Nayak" , "Gautham R . Shenoy" , Vincent Guittot , "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 , Adam Li , Aaron Lu , Tim Chen , References: <20251209112134.GK3707891@noisy.programming.kicks-ass.net> <58a92e45-3b43-4938-b10f-65f7fa7c5017@intel.com> <20251210151350.GL3707837@noisy.programming.kicks-ass.net> Content-Language: en-US From: "Chen, Yu C" In-Reply-To: <20251210151350.GL3707837@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: TYCP286CA0014.JPNP286.PROD.OUTLOOK.COM (2603:1096:400:26c::8) To DM4PR11MB6020.namprd11.prod.outlook.com (2603:10b6:8:61::19) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR11MB6020:EE_|CH3PR11MB8443:EE_ X-MS-Office365-Filtering-Correlation-Id: 13a5c535-54a8-43d3-0536-08de3847ff4a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?QTdKSGhOSTRvQWh1aklvVWIwV1ppekxIYzRTU1VDUzJJTXFPZUd0emVxSXRa?= =?utf-8?B?RkZTeHltSkxZTlNoR2dsbjVGOEo2dm4xZFUzQkpLNE9ZamN2enV5aUlQV3Ny?= =?utf-8?B?RTM5eXBWK0dUbmhESlpCRTNaa1hra1g3cm1STWlzdEJZMmJXUy9udTNZdGFB?= =?utf-8?B?NlYxVVNGZGRHNXNac2dDSDk2bEYrUmpmaWRXcVFZd1kyRW9hNmpWOS9PWGg4?= =?utf-8?B?THpJMVU1UEU0bGtVSGFnMjJVcWhrSlVvTmRIbVg4aThGN3RzR1JubG8rZ1Br?= =?utf-8?B?OTZ3ajlTZHhRUDcwYjluOHl0Mm9xQWUxWkw2ZFFKcWxPL201OURjM2FrZEJh?= =?utf-8?B?UUF6bHZZTXNUMm1HMm9ZNGQ0Nm1aUDkrcC9UUCtFWmJGVWQrUjdJT3RZNm93?= =?utf-8?B?SExEbWcxaVBidHRibitUOG1WY3hXMkFVQ25PN1RhODEvOXBFZlpSbUNrMzVG?= =?utf-8?B?RkkvNnZpWVYzendZYktzZUp6ZDdFVmtVTFh4dWxZNTF2a2xPOGcyRnJHb3I1?= =?utf-8?B?UHBHeUlyaTVJMmdzbUFIYWU2elNzeldRRnBGaE1QaDRTYlJrU3YxRFRyUEtn?= =?utf-8?B?VTFKSld0Slh0RUFDK2NsZ2pZS2lISmk0aHRCQ0dRM1FrRnE0ME1aaEhyOEkr?= =?utf-8?B?R1FYQitKTDBBN3cxQTUxZXhVQjBLM0x1WjlzZ2tubCtLK3Q4ZXEwcDNzQ0VO?= =?utf-8?B?aU94MWlkb0lwQ0N6cTk0RmhHUnBueHpYUkgxandxMnM3S3dVSGZGSlZheWo3?= =?utf-8?B?N045enBMQ0Y3a3puTEJQdG9pbm1xNHFuMTY1Q1ZweUFLckFvNjJlNC80VW9o?= =?utf-8?B?YWJEY2xRZ3E4OU9OdXJiNmZmR1EzUDc3cG1lcUpQMkJLcUttZlNRZGhZSDAy?= =?utf-8?B?ZXZ3M2x5Yy81RnYxKzdLMlNtNDZyMGQ4bEtjVDJ6T0lNRXhxbXRyTWNIMlRG?= =?utf-8?B?ejJHVWd0cVhzSXNpejJ1VGFiVER0aUxSQVJXTDRPNHZPLzVLRUdrRlZLeEgv?= =?utf-8?B?UGthUnJPQUlBamE0V01EVXd5TVJzT0FGVWNMWDZsWnRwcGIzY2dEUW9xTWlB?= =?utf-8?B?eUYrdkZLcUF1OHA0NXV1R0tjR2xsd1l2NGZ6SEYyR1pldFFiRThvdW80SVNQ?= =?utf-8?B?MldHK0NZZEVNUTZURHFhdU5DMEFoKzJIYTRQMGFkMHJVRWRSWEJrQTdJNjVs?= =?utf-8?B?YnNBQU50SkJEOHQ2NjFLZTgrSWVia3ZCd0l3QzN1WEVYb3BnQmFobE9YcHZo?= =?utf-8?B?bE5maWd5cWZ5NllGMDhVRzFYSkpQWXJEZ0pjMm9wY09GOHI4SmtXRWFOcTY5?= =?utf-8?B?eWd5RkxVWFl4R1kyMzFDeGlrVS83R2hjQnppRC9tSG9mcDl0S0xJTUIrN0c4?= =?utf-8?B?M05RUFB3TlhlOTBwcHhsVWJveE5wWlVRY2pOZk5EL2F0emxHeGk0VzRmaTEr?= =?utf-8?B?RDVGdVQzTVJKcVFrR1NLdHRWaDZwN2JFZmNEdDVaeFFsSVJ4Um1xRzVLbExx?= =?utf-8?B?SHQ3WEhMRC9mdVo0MnAybHJlcHpCZFlkc1p4aDYyQmQxYjFUdG9zTDZhM0lL?= =?utf-8?B?dlRXWXdSUnlnR1RJSTh3Q3l1ZDl3WEVablZZQzRMWmUyTklmVWVoV3djTDVh?= =?utf-8?B?ZTZPS3EwMmlVUUc2Q09NVUo5Z25ROHN5emVnZGlxK1FJT1RycC9JT05LdVZy?= =?utf-8?B?cFkxQnlZTUcyYXU5RWY2a2VCaWp2YzI2Mmc1KzVhdkJGUjVGcWsybkJ2TDND?= =?utf-8?B?OERpU0JWcHQwbXhRY3ljU3hQNDdTZHRFdWdNbkp1QXU3NExxV3VkZ1hmMWph?= =?utf-8?B?NTJaZ01MdW5MV0RqODJSRXZndk9SYXBhbGZJZjVhZ1N4aTdQNWVUbXRhTEVj?= =?utf-8?B?WkUyc0ZMUEVWNWpmTW91UEEwdVMzUCs1S2tlREMwQ045YkVUYnpadWZVUTdC?= =?utf-8?Q?rrPt+9T2o4R57U8xEczj5aulNH8nrIUX?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM4PR11MB6020.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(376014)(7416014)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?TFZYQ2w1OXlickhWdTdreGJHNU9XTFFOWGtVcjlwKzVzajFtRVA2Rmp0aHIy?= =?utf-8?B?WUxsWTFkS3VjNXg5aUpncUxjdGxHdy9NMnBzWUNqNXBRR0FOc1hmekM2WWJ5?= =?utf-8?B?bkJFbkNUV21sN0xtRHJzajhULyt3a0E5QWtFUWVvRjNWcHVPZzFCZXlYVzZI?= =?utf-8?B?bUllQmd1WllXQWdLWHVFTW9ENGpxdGJjSStiMWdZbVFBWXh6SUNUd1RERFdG?= =?utf-8?B?QS91eXVmaFpad3N4Mzd0R0tPZFUrMnE2MDQ5WDZGTG9Galc3YWIyUSs3Ymla?= =?utf-8?B?eUhtck43VnY2MGVTcEFZQ3RqNm51L2h4ZVVaMXlTNnFxVEpsWGJ3UmdvWm04?= =?utf-8?B?V2hTWE1pMy9vR3V6TEIvWXZXcW9rVmFqOHE5dFlZU1FvNXM1bzIya1VZNVRM?= =?utf-8?B?NWJQQ2toNzdqNSs0ekw0TW9oR2M0ODVtTjVqZURXbzRyZUZESlA2MGh0UjI3?= =?utf-8?B?ZzU5UFl0aUdMWU5qL3lUNDdaRDh6NEliZUh0bXBzcGJhd2lEL3BqZW5Ld1Fs?= =?utf-8?B?QitDTCtCNmxuUHFsNk1HYzhRRmhMUlJoNXp4Y25pUGcrVCt3VGRxT3RYYXFx?= =?utf-8?B?aWdONFluVFY0MTRncjM3VHRxaHYzQ25RTDJZeFI3U1hhdkRXbW5BK2RmcnpS?= =?utf-8?B?bEwrak1NWG9obFZtejFyY0lXbzlQSU16Z3VkSXU5Wm9KU014bTU2Q3lyUTNV?= =?utf-8?B?cFJhSHUzNVB0Q0IzTm4xbHRTKzRIS1hZYjVHK1NFVDMxeDNUaXltOWhYVHFn?= =?utf-8?B?dFFNQ24za3FEZE9SM3JSa2llWi95V1VRUXg1elZ2ZE04TXhzUlE5MUs4QUpX?= =?utf-8?B?S3RNWEkxVjNrbm1zL09lbnBRazBmYlZIdGcveld4L2J2a21LMEF4Mmg2NkE4?= =?utf-8?B?TDhaQVZLcjJLZTNXVm5WVHlROFdRdUZFc1E5T3NqdTBpNDRTeHF4bVM0T3lU?= =?utf-8?B?U2N2M0pub0JkU2xHNXdZdEdpNGVnZXpSTkpwYWJNZVE3RWhMWWIyV2xPZk14?= =?utf-8?B?clJOWVArejF0VkMycE8vNnA4aHdKaEV6U01ESEVTU1V3MkpBbnRDbXcwL0pG?= =?utf-8?B?dU1yZGQwTDhabFlFbjhBWEVUY1lNQUh5amF0K1FxRE41QVBlQURJYWlUQnJP?= =?utf-8?B?cUxhUkdHcUxZZS9weXVsRHlJbVJPSTJFa2w0TjJnN1AxSVMySzgxdmdWS2RE?= =?utf-8?B?SWZGZjV3OEZGZTlKVUV4WmtRckZJWDhUaFFqVksrSk9VY0lIQUtTQndnZmxY?= =?utf-8?B?eElrbVAxOFRRWlZRU0h2S1lzUWRrbXU2YTFuUDNkdzhndmxLVkFMaWQreEZB?= =?utf-8?B?aUZZRUJybTlQRCswWFcyZXd6eXFrYnNQUi9ZbmlQOVVjWmlBMlQ5K0MyNFVL?= =?utf-8?B?YVRPdFI3MUR6dVBYNEdkOVlHMVhNZTdOelFiVFF1ME5nQXZ0OHRKZG9sdGRF?= =?utf-8?B?aU04MnNyTU1CUWc1VDI1cStkN1ovTGFCaWV6YlVkakJhN1JremRjcTRobjRo?= =?utf-8?B?VmR6aWFWSTZHUmJVcExrTGVkcGRCbWFDMHZENGJMRFFNVlpFVjI0SStmUWRo?= =?utf-8?B?UDJlYm5YTTEyY3RPZ0oxUU43c1k0QThBMEx0UFQ0bzhETkowR3NJU0VROHZT?= =?utf-8?B?K0o2bWRlanJPUFI3MlpFdFgybWtBbHJodEM2VTA3RWtNM3pGL2VGZDRWQlpB?= =?utf-8?B?VVhvL2N0MjdnL1o0WTJBOEhTZ1ozRmRzVHowUm5OejA3YzU5dUNvdm1RZU9o?= =?utf-8?B?MGpGc294cmVvMGhvMVdQaVEybmtOVVZ1cG9yTFMvb091WlpvWFZYeWRqTTFC?= =?utf-8?B?NzNaZHJ2aEpXc3c3NTRwd1BCY2hWa2tTdGVycDJGLzlYalFoM2t2ajRoeWpY?= =?utf-8?B?eVBqSE0vUEJyZ2FvME9GeTMrWWE0RUZ1TXdiM1VhWkZwRUE5TWF2azBPV1d3?= =?utf-8?B?N3hRajZuYTRrSTViUGRQZFhRUkJ0cDFRYm9mOVUvbzluaERBTTh5YTdZY1RR?= =?utf-8?B?dzMwa1B3aG54RjM0eWpLR2pMcnlCWlBjSE1CbkNNREFiaGV0RjJQcFdXd1Jr?= =?utf-8?B?SUg2eTMxWnJmT1lSaGc2a09TN3BUWHVzaXdxdURYMUNnM3d2NVZ1VFd6N09p?= =?utf-8?Q?7PGCS87tDeppYX4jN/YVjSNKI?= X-MS-Exchange-CrossTenant-Network-Message-Id: 13a5c535-54a8-43d3-0536-08de3847ff4a X-MS-Exchange-CrossTenant-AuthSource: DM4PR11MB6020.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Dec 2025 23:58:21.2232 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Fx9exW+4HPknVdXGc1G+Ooj6KHx1QAr1Sxj4sfS0bAdiMTQAyVI0dKEUFJbsO+oJCsLBDA/BqCHpjtkWC937jw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR11MB8443 X-OriginatorOrg: intel.com On 12/11/2025 12:13 AM, Peter Zijlstra wrote: > On Wed, Dec 10, 2025 at 11:02:39PM +0900, Chen, Yu C wrote: >> On 12/9/2025 8:21 PM, Peter Zijlstra wrote: >>> On Wed, Dec 03, 2025 at 03:07:21PM -0800, Tim Chen wrote: >>> >>>> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h >>>> index bbcfdf12aa6e..0ba4697d74ba 100644 >>>> --- a/include/linux/sched/topology.h >>>> +++ b/include/linux/sched/topology.h >>>> @@ -68,6 +68,10 @@ struct sched_domain_shared { >>>> atomic_t nr_busy_cpus; >>>> int has_idle_cores; >>>> int nr_idle_scan; >>>> +#ifdef CONFIG_SCHED_CACHE >>>> + unsigned long util_avg; >>>> + unsigned long capacity ____cacheline_aligned_in_smp; >>> >>> This cacheline annotation confuses me, see below. >>> >>>> +#endif >>>> }; >>>> struct sched_domain { >>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>>> index cb82f558dc5b..b9f336300f14 100644 >>>> --- a/kernel/sched/fair.c >>>> +++ b/kernel/sched/fair.c >>>> @@ -9622,6 +9622,29 @@ static inline int task_is_ineligible_on_dst_cpu(struct task_struct *p, int dest_ >>>> return 0; >>>> } >>>> +#ifdef CONFIG_SCHED_CACHE >>>> +/* Called from load balancing paths with rcu_read_lock held */ >>>> +static __maybe_unused bool get_llc_stats(int cpu, unsigned long *util, >>>> + unsigned long *cap) >>>> +{ >>>> + struct sched_domain_shared *sd_share; >>>> + >>>> + sd_share = rcu_dereference(per_cpu(sd_llc_shared, cpu)); >>>> + if (!sd_share) >>>> + return false; >>>> + >>>> + *util = READ_ONCE(sd_share->util_avg); >>>> + *cap = READ_ONCE(sd_share->capacity); >>> >>> You placed capacity on a separate line, forcing the above to be 2 >>> distinct lines. That seems... sub-optimal? >>> >> >> The reason capacity was placed in a separate cache line >> is that writes to capacity are not very frequent(cpu hotplug >> should not happen too-frequently), while writes to util_avg >> tend to be relatively frequent(changes frequently). >> If capacity and util_avg were placed in the same cache line, >> I’m thinking writes to util_avg might invalidate the entire >> cache line. This could potentially cause cache misses when >> capacity is read elsewhere, which might lead to false sharing? > > But its introduced here and already read/written together. Is this not > premature optimization? I see, since they are read together, there could be a pre-load of adjacent cachelines I suppose, I'll remove this cache alignment and check if there is any performance impact. Thanks, Chenyu