From nobody Mon Feb 9 11:47:00 2026 Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) (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 B67FF6F08E for ; Tue, 28 May 2024 00:37:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=205.220.177.32 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716856630; cv=fail; b=c5kMvigwyAk7fFeekbNFQZuutuIHy2EhsEKbVNvcS6hjTNVq4aMfYfr3Vz0kfvnVCDTpvwO0xcNYiJjJG8btj7QW2VWyPX/qedIxD8QsM8fK8D7mh9iomJVn9jUWOAUDsnK8jPqoi+Ojceeqljvm8du56ONXBjbx1VSstIh3UR0= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716856630; c=relaxed/simple; bh=hXHkzwWWOUuAqPF0DyTa+EsHAXTodmn+MHLeM+Ijy3Q=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: Content-Type:MIME-Version; b=pifLk1Hpv9nDYjvhY7PjgirKE4q7zY9AfELBLCDIN6Xddo6mjGO8BEy1ffpy36ryapgTMtPMJB7dumULm8dGjo4x6ulb6udc5WD1PqQaJZ/YdJYNZJkoz3l7NeEKuudAqsooxysQR/iajxfG7HEjowpC7zM6Cfi1zCqr2SdpTp8= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=oracle.com; spf=pass smtp.mailfrom=oracle.com; arc=fail smtp.client-ip=205.220.177.32 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=oracle.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=oracle.com Received: from pps.filterd (m0246631.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 44REO8XC025939; Tue, 28 May 2024 00:36:50 GMT DKIM-Signature: =?UTF-8?Q?v=3D1;_a=3Drsa-sha256;_c=3Drelaxed/relaxed;_d=3Doracle.com;_h?= =?UTF-8?Q?=3Dcc:content-transfer-encoding:content-type:date:from:in-reply?= =?UTF-8?Q?-to:message-id:mime-version:references:subject:to;_s=3Dcorp-202?= =?UTF-8?Q?3-11-20;_bh=3DJMn2ecYYBoWtIlbNIVynYrtc9Wkxo+prgoaPHIFnEv0=3D;_b?= =?UTF-8?Q?=3DYe05VhHSXLQSeB6LBeY2zQ9OPa0K23e9l1Ep8Ab9qPqy1YhUtI5iuNqJUeEj?= =?UTF-8?Q?rAHpfWNb_h5pKEWGJZt4nyjzagVsNzX4N6XtuxzboBSu6npb2mvaZyTl2ygFiHK?= =?UTF-8?Q?378IWzcfPh9342_IF5WuLF4wJgkyIQY1rMC1QmuDymngViOo7KQKfdrP7tFH8WP?= =?UTF-8?Q?rhY75bLvrbx/3NTshcF4_VadYmQ/iwj8Qwj5jAhIJUcprPUDXyYWnSlHwge7IQN?= =?UTF-8?Q?0MXL9Fq6Y/PxPrnVuC7tSoB9nr_GjDN+tiVkBXYoqn9dp4saQfAgcZspjhyKVmm?= =?UTF-8?Q?gqJdOGK2bzLiXzTWrjR4otZ3yjGUjn46_4g=3D=3D_?= Received: from iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta02.appoci.oracle.com [147.154.18.20]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3yb8kb37rh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 28 May 2024 00:36:50 +0000 Received: from pps.filterd (iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (8.17.1.19/8.17.1.19) with ESMTP id 44RL5YJc037288; Tue, 28 May 2024 00:36:49 GMT Received: from nam12-bn8-obe.outbound.protection.outlook.com (mail-bn8nam12lp2169.outbound.protection.outlook.com [104.47.55.169]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (PPS) with ESMTPS id 3yc534rdy3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 28 May 2024 00:36:49 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=CgEtQVuFinjhiKNyWipzw3BteK8MYQitp5s8ljQsd5xqwF6HY4ozZfl9KZaXXqAHwkwGhMNIlb6xMVtaRPlHqnZtKNEOY4bIBtMAgmNuORahpOFGj1apV52uS3DiNFqIMTVvKrhQihTtVcctmIACVIFFNhCbUQ42L1wwss+iB0ldWHOVES/vf3E1roqhq14G9loViORqXPHShC+X+d16p9i8TVWZagz537PmIvBBWeQ4JxK9gBx1ufpqHcWi/ttWPKso8WRqTVvbziq+jNpvOvDv8D124T43D6nIMGqoAMxV6nDb967+iLvUIoHCgmDpHgD2q5hVAQYuzifLszJQNQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; 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=JMn2ecYYBoWtIlbNIVynYrtc9Wkxo+prgoaPHIFnEv0=; b=OWxj4TIDSmMMrA21Z9r4yIcSJ4jRDfD70kKObYJvfblBzJcFcWabb03F5lHRIPwSES5N1NsaYTom6aUL1+0z20Ug9UiwXWhfJ6X6NIVZtHM1+x3kllKn/FJ2Wl5Y46q/3eJkSgRAZGcp1oj97sVJSBQkEfcvhaW+SZLBoiwEi7SgUshae2pZix2BSTKvY6HWdQ52YSCWn6YEXhUaHs++dR+ZQUXkTnYGTqWMT8DPQ3lEJ/u9D5PjsjQJVqp0S7V3F4YuoaO3EEueP3p9I76ieLTYfr+KEct9NvNBm2nP3Q/UuqMHk+Bu0BOmR5V2Zc90Fc2lbE6icGWB4/IoUv4uEQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=JMn2ecYYBoWtIlbNIVynYrtc9Wkxo+prgoaPHIFnEv0=; b=r87R9hXTp1gsC2u8f3YFaftK5GtLqI1dfHl6v3ptqBDwuRLyiz0a0ExLKhfUF2XEXXDfyOiFkoXvnWWclhZ0hpOD5WBljoGUopwc9WzcmPAwGBKa/JqD71KtlLybRUgtTIy/6JyDvwte+R6sbhQTMDSli/jYU+ypAwCJby9sIv8= Received: from CO6PR10MB5409.namprd10.prod.outlook.com (2603:10b6:5:357::14) by DS7PR10MB7177.namprd10.prod.outlook.com (2603:10b6:8:e1::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7611.29; Tue, 28 May 2024 00:36:47 +0000 Received: from CO6PR10MB5409.namprd10.prod.outlook.com ([fe80::25a9:32c2:a7b0:de9e]) by CO6PR10MB5409.namprd10.prod.outlook.com ([fe80::25a9:32c2:a7b0:de9e%4]) with mapi id 15.20.7611.030; Tue, 28 May 2024 00:36:47 +0000 From: Ankur Arora To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, peterz@infradead.org, torvalds@linux-foundation.org, paulmck@kernel.org, rostedt@goodmis.org, mark.rutland@arm.com, juri.lelli@redhat.com, joel@joelfernandes.org, raghavendra.kt@amd.com, sshegde@linux.ibm.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, Ankur Arora , Ingo Molnar , Vincent Guittot Subject: [PATCH v2 27/35] sched: support preempt=none under PREEMPT_AUTO Date: Mon, 27 May 2024 17:35:13 -0700 Message-Id: <20240528003521.979836-28-ankur.a.arora@oracle.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20240528003521.979836-1-ankur.a.arora@oracle.com> References: <20240528003521.979836-1-ankur.a.arora@oracle.com> Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: MW4PR04CA0233.namprd04.prod.outlook.com (2603:10b6:303:87::28) To CO6PR10MB5409.namprd10.prod.outlook.com (2603:10b6:5:357::14) 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: CO6PR10MB5409:EE_|DS7PR10MB7177:EE_ X-MS-Office365-Filtering-Correlation-Id: ec331fbe-be2e-4bb1-c293-08dc7eae41f0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230031|7416005|1800799015|376005|366007; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?fu1zVSJL0z185NBgtEWNJFTpigkIyG+Vj0pN2YD7iSVUNP85n5Drt9UL83Bu?= =?us-ascii?Q?obTgxE+5Dtq0bkMOE+V1JskRUXvoY3tljsHCUxugEQhbn8mMm1/DYk7uYGzL?= =?us-ascii?Q?urIZuFQVJ28x8RMQn5IX6+F15M1S6lpRHbnEEBoaVipuYVdyS+sSCDoYxGNH?= =?us-ascii?Q?Zwfh8ODe9jg7od/4XhWXT8J3Bytva4JY+BbuA8bd2TQfDlueMWi+pP9QyqIK?= =?us-ascii?Q?ejuZixJ58P42Ttfn4gSouLqbCym/fYqvB9uFRh4oW2CfuCgrQLv5agFjl0Oa?= =?us-ascii?Q?kHRUdUb3xxM1qS3ost+Umihf6JE/Eh3JPtcKgDb5ZEC0X2V0ZqyDl3YP2FjX?= =?us-ascii?Q?h2dmP0cvzEBqQUg+RiZvyr+16X8KebAQlk3t7IN4fyBgXZ0hSGOh30GQi1Br?= =?us-ascii?Q?uh/zFl3F1yDv0l5HJeCdeSONvSlsHFBn7tKmIl9FfaJEu6Scxlgm/d0zE2ld?= =?us-ascii?Q?zMUz33gDkIdJeXzBU9nJoDr8//S4PKpVyQWwS35P1sYDssEJoJIpjDuSOqE9?= =?us-ascii?Q?zeRpdzuGJ2hm+9MnIKcY0czQ4WLXO/9LSPMyTdLbNWOaYOSKC0T76VOeUfAc?= =?us-ascii?Q?3ZKAizEYP27PQs/B4pY7T9T5fpxFpT7aOl+Zcj3Yb/75Tnt4ZJ9h8SJRLLAD?= =?us-ascii?Q?w0lEc58SlLiaLRbZRmUI8plEuNS/s2t/mMBfZJMqBUSFD421Jj/p4DDFxnLO?= =?us-ascii?Q?mnvvKA0H6ATybmISoW4OcI1R9mNa/WumQgDlRzAqcPKDcLuq9uZdjLb3Pjsp?= =?us-ascii?Q?fU1uo0EvSTVLVq1hyy8VY15nGfvz2EpkPz/8KL/mIkbSU9eTJWk8ldVL8Wu/?= =?us-ascii?Q?4/5zW3TtPdTlXrYjYWw4HvFseBfxYwPwW2zoyAE/HeRHd3AN/0a+xGr0Q1Qu?= =?us-ascii?Q?tPEwDbLM5omSDwXfdDgFrdaGVmo2iA/+xx2s77gtLlG5lT2tNvOg6TjTYRa9?= =?us-ascii?Q?CQZrPphiRj6+AXXKdKULjt7gIk4Rvsn6jH2X3XYIAYf/0MhsJ7M4Jm1XtgqB?= =?us-ascii?Q?z7zPnFryQAa0lwCppbw4uIpMNx0aGxltPw70i+PDB9HYk+WQAxRPQmDGQ9CG?= =?us-ascii?Q?3YeGgzmcMoS8Sh1I8hrlnJWeGdyJWZjlkcxErbCVV46XNZWZkHpynDEXiJvJ?= =?us-ascii?Q?dvTdfcc2zXQMztMXVhU1vqbzzJF88O+sOLhZX/rMqwg1hB+62jJx79mGBlPt?= =?us-ascii?Q?vuJ3ABPusoCLqkPVEhyJFVqKTkR+yGEMWwz59g=3D=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CO6PR10MB5409.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230031)(7416005)(1800799015)(376005)(366007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?uvODp1dGEtgPYAvbJ/XrB6Rd3A8y1WngNW2PmxHMmzyTMxw4TA+vrsYNf/Kc?= =?us-ascii?Q?n9rPehDILyDbl0Nhn4Jd7Spbl7qUxq00Phycd5Z+eC56q6my/0gyxzzzf5bC?= =?us-ascii?Q?5EDkWM8s/ke/fYTkS5fB1kHsw9rpQ9dgkMGSSCc8oiFCK7G6cXrlzrf7ZJT6?= =?us-ascii?Q?++voxryM+nuWRX5fDxByt9QRHck5EVQkwmn/XxL4aVUacFptzsfILLSAsqKB?= =?us-ascii?Q?EO7+4v4LDKSSlyi8nnSn/qK6zxZ2bQ9XlF5mgiPtVJWuzv0MdWoZnSUHcD5a?= =?us-ascii?Q?w5Et/UUUdIUGfekEfB/yfS9trcXdsFuGX+bF0wQahK64oMBV19rlbk8Ase6x?= =?us-ascii?Q?AObH2oD0dKE/0Kc5GljTB/3DVPdORU3xG3rTwhURZUaRYEoQ3RVNX5ykVG5p?= =?us-ascii?Q?avQ36r/EG91JDsDEw/KXctjo1ragBWfnnxdownqPNs8cVY2LSehvuAGHAblL?= =?us-ascii?Q?H7KHoDdcri7ooBOhdUFBJmHlymMhP2Nizr87cbShRig8Ewpvy60IooD2EPyv?= =?us-ascii?Q?vBb7KANEbB15X3DY8rTIX/1OjuxFOTQdgYboUaXCbOExgDgT5k36vkdOieMi?= =?us-ascii?Q?mVGQy6I6XnS1qH6nf74mVmnqlVVJnlTP6Wdj4ZmFlpZ0gQdsx6HoRxA3I4Xm?= =?us-ascii?Q?5JO7xFb/fn+xPdCuq6ajfPvbZGrnTW8Y2i3KSN6phajvr7J1KU50wlDd/wB5?= =?us-ascii?Q?c4Tq6s8cSSmHHD2H4vV2TRwKdv/7hqwF92SAe8H4zFaD3KWdEi6ehUBwJNnZ?= =?us-ascii?Q?Wn8f6KxtLFcIMMSVlZAZM0kVF8PI6uKNDsoFR8ZxGc3d7CqzomlYC+hBCNh7?= =?us-ascii?Q?0ZrQ1HISlMP8d/ohlxs8xAjyEdZHeBgOkstyLMgEx7RawYNLjBjeknOrvrnc?= =?us-ascii?Q?mdr21DbDdagyKxmvMwJTkCe9ETICjtyc0Au33RULR327/6ibMMkOA/QGb457?= =?us-ascii?Q?TA+uW3YmIAzCjif9LVFZGrWEExVQlFFjqq5Y6nwFBgqZgVcR7dpNLugx5JdD?= =?us-ascii?Q?psDFDEc6VRBg003sbUYnKUQUQJiXvqAOo488XaoTopfnWGHWWbWtHcsFWxSL?= =?us-ascii?Q?DS1evS5ZiK3sPCU+3PbjNw98/eAIYKyQ8kumB3ndaasPnHlMkD2M5DTsK31X?= =?us-ascii?Q?mpvFvVxwv78gAeXBAZ01moXLwFe53U3t8Nkk7hFHwe8f3FqrZ6A5rxR2pHG7?= =?us-ascii?Q?WJVIBndKR0RWBOeElQCmVaym3wZd5uZpsdPjOIaM+2ZpJK//CIdik04BGoDT?= =?us-ascii?Q?GlyFF9+py5P2jC3i9lIOn4yW4IbVpusSVG6tkqD0zaBm4R22VZxGd5Y0Zd+I?= =?us-ascii?Q?BC1eSF9iqewlGTZFlseH7a37GwVNK59cFxZk9b/qnLN9FQsiT/+VoOzd+1iV?= =?us-ascii?Q?jPEcyp05Durvt8OE+9ARPVB68L8V9z4H/SN+8lehVE1rwZGDIlhdixyHdqjm?= =?us-ascii?Q?b4mUGo9wYWwEBiRE1qhI5UT8BqfNtKp6EXrzmNfOyF1my+j8zVkQkD91NBuD?= =?us-ascii?Q?k5p67xhRcGGGXej0m6MTyOUbW0UZBHGgkSpXtDkKDRLyq75mUOs85aUpoxRn?= =?us-ascii?Q?euaafhNn7LJPYOyJLUAjuOqNve+kNf0omcyb+Dikf84XOel9DfVZBkQ5qtbn?= =?us-ascii?Q?Mg=3D=3D?= X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 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 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: ec331fbe-be2e-4bb1-c293-08dc7eae41f0 X-MS-Exchange-CrossTenant-AuthSource: CO6PR10MB5409.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 May 2024 00:36:47.6857 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: b+cWVn8aGU2d3GeFTKI66FUoK/sLq8uTHCyQn60If0aZ1PvAG/W+v/A7W/5F4t4cyaLRHMpYRewaO3XHFkVHFq5N6fIJatEXHkz4yJOCtlQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR10MB7177 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.650,FMLib:17.12.28.16 definitions=2024-05-27_06,2024-05-27_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 spamscore=0 phishscore=0 bulkscore=0 malwarescore=0 adultscore=0 mlxscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2405010000 definitions=main-2405280003 X-Proofpoint-GUID: slSKCrZ9TwzEFCoomCc9P_MakVGV_Go0 X-Proofpoint-ORIG-GUID: slSKCrZ9TwzEFCoomCc9P_MakVGV_Go0 Content-Type: text/plain; charset="utf-8" The default preemption policy for the no forced preemption model under PREEMPT_AUTO is to always schedule lazily for well-behaved, non-idle tasks, preempting at exit-to-user. We already have that, so enable it. Comparing a scheduling/IPC workload: # perf stat -a -e cs --repeat 10 -- perf bench sched messaging -g 20 -t -= l 5000 PREEMPT_AUTO, preempt=3Dnone 3,173,961 context-switches ( +- 0.60% ) 3.03058 +- 0.00621 seconds time elapsed ( +- 0.20% ) PREEMPT_DYNAMIC, preempt=3Dnone 2,942,664 context-switches ( +- 0.49% ) 3.18924 +- 0.00483 seconds time elapsed ( +- 0.15% ) Both perform similarly, but we incur a slightly higher number of context-switches with PREEMPT_AUTO. Drilling down we see that both voluntary and involuntary context-switches are higher for this test: PREEMPT_AUTO, preempt=3Dnone 2286219.90 +- 39510.80 voluntary context-switches ( +- 1.72% ) 887741.80 +- 20137.63 involuntary context-switches ( +- 2.26% ) PREEMPT_DYNAMIC, preempt=3Dnone 2125750.40 +- 29593.55 voluntary context-switches ( +- 1.39% ) 816914.20 +- 13723.46 involuntary context-switches ( +- 1.67% ) Assuming voluntary context-switches due to explicit blocking are similar, we expect that PREEMPT_AUTO will incur larger context switches at exit-to-user (counted as voluntary) since that is its default rescheduling point. Involuntary context-switches, under PREEMPT_AUTO are seen when a task has exceeded its time quanta by a tick. Under PREEMPT_DYNAMIC, these are incurred when a task needs to be rescheduled and then encounters a cond_resched(). So, these two numbers aren't directly comparable. Comparing a kernbench workload: # Half load (-j 32) PREEMPT_AUTO PREEMPT_DYN= AMIC wall 74.41 +- 0.45 ( +- 0.60% ) 74.20 +- 0.33 = sec ( +- 0.45% ) utime 1419.78 +- 2.04 ( +- 0.14% ) 1416.40 +- 6.07 = sec ( +- 0.42% ) stime 247.70 +- 0.88 ( +- 0.35% ) 246.23 +- 1.20 = sec ( +- 0.49% ) %cpu 2240.20 +- 16.03 ( +- 0.71% ) 2240.20 +- 19.34 = ( +- 0.86% ) inv-csw 13056.00 +- 427.58 ( +- 3.27% ) 18750.60 +- 771.21 = ( +- 4.11% ) vol-csw 191000.00 +- 1623.25 ( +- 0.84% ) 182857.00 +- 2373.12 = ( +- 1.29% ) The runtimes are basically identical for both of these. Voluntary context switches, as above (and in the optimal, maximal runs below), are higher. Which as mentioned above, does add up. However, unlike the sched-messaging workload, the involuntary context-switches are generally lower (also true for the optimal, maximal runs.) One reason for that might be that kbuild spends ~20% time executing in the kernel, while sched-messaging spends ~95% time in the kernel. Which means a greater likelihood of being preempted due to exceeding its time quanta. Cc: Ingo Molnar Cc: Juri Lelli Cc: Vincent Guittot Cc: Peter Ziljstra Originally-by: Thomas Gleixner Link: https://lore.kernel.org/lkml/87jzshhexi.ffs@tglx/ Signed-off-by: Ankur Arora --- kernel/sched/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2bc7f636267d..c3ba33c77053 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8983,7 +8983,9 @@ static void __sched_dynamic_update(int mode) { switch (mode) { case preempt_dynamic_none: - preempt_dynamic_mode =3D preempt_dynamic_undefined; + if (mode !=3D preempt_dynamic_mode) + pr_info("%s: none\n", PREEMPT_MODE); + preempt_dynamic_mode =3D mode; break; =20 case preempt_dynamic_voluntary: --=20 2.31.1