From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 94AEFFF5136 for ; Tue, 7 Apr 2026 20:09:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 432F46B0088; Tue, 7 Apr 2026 16:09:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3E4876B0089; Tue, 7 Apr 2026 16:09:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2AB9A6B008A; Tue, 7 Apr 2026 16:09:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 189C56B0088 for ; Tue, 7 Apr 2026 16:09:39 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 517D65B9C4 for ; Tue, 7 Apr 2026 20:09:38 +0000 (UTC) X-FDA: 84632850036.25.6F61B74 Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) by imf06.hostedemail.com (Postfix) with ESMTP id B8745180006 for ; Tue, 7 Apr 2026 20:09:34 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2025-04-25 header.b="lOcZCTV/"; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b="SUAA5a/C"; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf06.hostedemail.com: domain of joseph.salisbury@oracle.com designates 205.220.177.32 as permitted sender) smtp.mailfrom=joseph.salisbury@oracle.com; dmarc=pass (policy=reject) header.from=oracle.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1775592574; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding:in-reply-to: references:dkim-signature; bh=Nr59LrE8x3EgL6B7A9E+zTsBrMUaqhqUWIbktxE14yQ=; b=G/Wzbbz1XlTrq3BmxtIo3fM7o0FIUAeqyZSFMrIX2Pg0XJExtGBzcxrGxdRFcpFIKse24+ Qnd2QG5HG0gX6vAjFW5kFzx50u6R3UTcfFBHIqfqQWe+zjgD4Bh/QrhA0WZ+uwEW0YotI2 5yD827VuQazhDUhGkggqC8hfeFIUpdo= ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1775592574; a=rsa-sha256; cv=pass; b=gzXd55IZDNeEB4aqt45JnQptjYyPAJNDOu7zllpyzRvNjBdGAx/8Uhf2gEefeHdFqBn+Bk +6Tx2Af0ycc40KBFofQrZv/yuMEq5aEgm+Pl2XLmrREbI7zqPGM7LcgTLdGBK0rQB71nK5 K8DCdvH9zSX3EusibvADHu2Zb7J8b80= ARC-Authentication-Results: i=2; imf06.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2025-04-25 header.b="lOcZCTV/"; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b="SUAA5a/C"; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf06.hostedemail.com: domain of joseph.salisbury@oracle.com designates 205.220.177.32 as permitted sender) smtp.mailfrom=joseph.salisbury@oracle.com; dmarc=pass (policy=reject) header.from=oracle.com Received: from pps.filterd (m0246630.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 637FL9ek987852; Tue, 7 Apr 2026 20:09:26 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=cc :content-transfer-encoding:content-type:date:from:message-id :mime-version:subject:to; s=corp-2025-04-25; bh=Nr59LrE8x3EgL6B7 A9E+zTsBrMUaqhqUWIbktxE14yQ=; b=lOcZCTV/VqPQYsQfqb6l67jCbIhjGDsD D7aKq08niE9W+TW2QxIwxjniUeIvfqJjf6IkpTVQXqqY5iQVJNzt2J6F1Y6zwxZ9 BWYgrJm3EmTVoqNHbad4WNlQb5wZmXyZoTLLgH7U0vFYMUnCJ1aKQpMSoPal946f yxDo91eXTddCTPSFhnqwrDUNQ3yfXlRb5wmrfzFlcl5kiCEAwnZd8clceUrw1u9/ Q+LoR3ylRAIwj9+NV7TLVZfqNPwuPmq2ewC0HVOKpodDCqs40ctUN5CsG+5pVJRh D6Hm1g9qk80MsdnYDDEBjqASN9On6p81eR4RFF4jR14C+E/mibvvpg== Received: from phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta02.appoci.oracle.com [147.154.114.232]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 4dcmqea5dg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 07 Apr 2026 20:09:26 +0000 (GMT) Received: from pps.filterd (phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (8.18.1.2/8.18.1.2) with ESMTP id 637JAJcV029159; Tue, 7 Apr 2026 20:09:25 GMT Received: from sn4pr2101cu001.outbound.protection.outlook.com (mail-southcentralusazon11012005.outbound.protection.outlook.com [40.93.195.5]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 4dcmq4b8tm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 07 Apr 2026 20:09:25 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=FgDqFpI3i0plqPBlJgkp/lb24LlbGWYGwmYzJq05jLt4AL0xNYJ/ZafB/CBoeS99UgfizoDQrUN5YsOBJXQRfS3R1rD9F5ipdOWZIzEwaVEGBla9gh86Vu2xinXVzTIFOVW0k2JM25c2h+cmZ27c9hvpQ/QV4WowUln+GlDHdJ9Zuzh4sPanCAfnx4FVEoGS2RWiFCsyt09wSzqcVQsWBuxstORwug0na6zxqufnQaXHvX5y+qL77U4/4kHBTTyNCQ4aidMO2Y61Zt06G86E8GSLwh7UDmTU+6Jv1XGXidcS+wYHKQ+ca4OckKbhLD9ghptU3rZQ0rV8PfVuzDcBcg== 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=Nr59LrE8x3EgL6B7A9E+zTsBrMUaqhqUWIbktxE14yQ=; b=amtx4GN7AAnJuXFnySewLcjlV9jTabRHZ+YJcq3vBLIOttQYmGDv1Nr/3rytYlZJTO69b3BBC8NEIk8tthyfEJI7UuSx/PDvLUkZ2HMfETkclH5gL/pot3W+eimn3CeCs/FTRmewLRlC5T8Z1JebvJdjMoSgN7+DTeSAnXOHV7uss5sZO3gP/VtObWGWburYigEivkRfhRRG7wLzarGcScHTUu4GUOBSUZ5g9IloZUXDiXoDzDDiNis/cqXVKmEySAAQNhXJTwKvaSCR938WSMVp0qdHuSCDu3VuYlmtV2IHOmFlctYeMWgdip48dsXcFDhYxN8wqTEz7Nq0U5xBXw== 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=Nr59LrE8x3EgL6B7A9E+zTsBrMUaqhqUWIbktxE14yQ=; b=SUAA5a/CJLPoUaJHLZsfN5KpY5+0ggj5wFrlC7x4VjW9DVtyIAcfWdeAkF115gtW2aivJoFB/G8HbJcM8D3AHrbq/rtipzDTDT9cH/kELDPX+83lyIQSE++6oHhX1Gs/bcC7N35uEwgSA72GmeVr73kVb89M/8a3v/zbIGHEtPY= Received: from CH0PR10MB5131.namprd10.prod.outlook.com (2603:10b6:610:c6::24) by MN6PR10MB8022.namprd10.prod.outlook.com (2603:10b6:208:4f7::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9745.38; Tue, 7 Apr 2026 20:09:22 +0000 Received: from CH0PR10MB5131.namprd10.prod.outlook.com ([fe80::ab76:24ce:816a:8307]) by CH0PR10MB5131.namprd10.prod.outlook.com ([fe80::ab76:24ce:816a:8307%6]) with mapi id 15.20.9769.014; Tue, 7 Apr 2026 20:09:22 +0000 Message-ID: Date: Tue, 7 Apr 2026 16:09:20 -0400 User-Agent: Mozilla Thunderbird Content-Language: en-US, en-AG From: Joseph Salisbury To: Andrew Morton , David Hildenbrand , Chris Li , Kairui Song Cc: Jason Gunthorpe , John Hubbard , Peter Xu , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , linux-mm@kvack.org, LKML Subject: [RFC] mm: stress-ng --mremap triggers severe lruvec lock contention in populate/unmap paths Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: CH2PR18CA0050.namprd18.prod.outlook.com (2603:10b6:610:55::30) To CH0PR10MB5131.namprd10.prod.outlook.com (2603:10b6:610:c6::24) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH0PR10MB5131:EE_|MN6PR10MB8022:EE_ X-MS-Office365-Filtering-Correlation-Id: cf5f41aa-194b-45aa-857e-08de94e18eeb X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|7416014|366016|56012099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH0PR10MB5131.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(376014)(1800799024)(7416014)(366016)(56012099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?K2tidndQUDZNY0dVRGRSVllrNTRPKzl4NWJwS1ppMUU2bGRYaE9vSGdvNERB?= =?utf-8?B?ZTNmaHRMb2tscTVoUTlDYmZkR01HS0lIb3BWa0thb1RjNVEwQm5oOXI3YVli?= =?utf-8?B?QU9oYUhCOXVkMEh0bjJsNTVoUHNpd2RKQnBUTk5qRERZaG5hR3h1ZE1KQjZD?= =?utf-8?B?NkVaakZxT2pHSFdBckt2Tkljc01yMlh3bjlnOWJXQWtXdE51Rkh2NE55dXA5?= =?utf-8?B?VW1aU09yM1IrMDI2dHNoU0RkcVRIUTY5OEtSTFlYRnZPTEtUbVYwNUgyblpX?= =?utf-8?B?dDdsbmhJU25lc3dLaU85S2pkWW03cSt3OWVOY3FkbkRJa2pFOHg0VFQrMEFD?= =?utf-8?B?ZmE4MGFGbTUzU2J5dzhES1p4ZVpDKzkvM3JTdkE3R2hOU1VoQ0l2cTFlRjZB?= =?utf-8?B?ZDZwK1Q3c1FFMmd5YmJmcGZCcWhWNXZBd25VS2l5T0RIS0cycXRBQU10TTVE?= =?utf-8?B?OUs4RDVxeU92NmRueFFlNkdtb3lwK0V4M2tJRGpCbXlVRDgwQjA4eHI1Y0JC?= =?utf-8?B?QlYycldXRHdMWWFKdS9lNnhQUThUWFVhV3MzTXN1a3Z1dE13Q2RQM0FnL0pN?= =?utf-8?B?RjdNb1IzMUpBYUJPbTBVZlllRzFtTU1US21IVUg0UjhWU0tkaWlITXNEMjZk?= =?utf-8?B?cUF1M0hmYkhCSDEvK1NOait6dDhIRjQyM09uaVpyTzhOSjBjdXJIZis3Z1JT?= =?utf-8?B?dTJrWHgyNzZ0NlUrVFdLZXRJRE1laUVXUkRGUGhoT3dnU3BONFBFTW81aThQ?= =?utf-8?B?aVRDL1YwNThSMDhiTUxUck1SLy9uay9jVUZRZmpKUmNZaWJSa1Qzclo5eXRm?= =?utf-8?B?cEhuNThoSmdqQ0p5bHowZC9UOWxkdGt0T0dHcHE1M1cxdS84alhsbGhkaXA2?= =?utf-8?B?M0kxaWhJTjZheldWV3VGNTRXSlNBdGw1alBtZW00SUFGRzZieWhrWE9ia2U0?= =?utf-8?B?S2ZWMGd1WGxpTEZGZk0zdXdCRHpuSUEwcVpKSkpycFc1YXdWbkR4M3krWlNH?= =?utf-8?B?VmRRbFNVTXVuUWw5dCtxSHI3QXpCdVNjM2k4b2UzaFo4cWdwYnhhc2lKbEE2?= =?utf-8?B?a3JOSEpQOVlhSHcxZ3N0b2JSeXdJdlZYT3NHQmdkVjB5aXlybFJ3ZFNEeVJu?= =?utf-8?B?bWlGdUMxNG41d0hONTNJRllvMit1N0FoSWZwdWxlcHZBVXBGTE50bG9GMU8z?= =?utf-8?B?OFIrU2g0MHg5Rlk2U0FBWXo4bE85cUJoNWtrVVFQSGpMVlYrUVRBZXpxTGQ3?= =?utf-8?B?RUQ2MEU4YXZIY0M3RktSQVRjTW80c2JnT3NnOEE2M25XTndYalhJRTIvTHA5?= =?utf-8?B?UHdrV1hrWldBQXJCSGtHYU1vOTQybTYyRUhxSWNEOHVsbzRFSmU5Q2RycTVw?= =?utf-8?B?NWtiOU5VVWp1QmpEVWIzeVpzWmRBRlI5Ylo1ZG1qa09yUHJtb01YRHZTNmJ1?= =?utf-8?B?OE8yMVduRklzbTZHR045YlJrTmV2QWFPOEt0MnJrNmh4L2ZXbW5QMDRyYjk4?= =?utf-8?B?T1ZFb1o2cmZrQmNLS01zUWo2NWNXb2pQU29MdU9Va2xJRFlZY0IvUzZZK25M?= =?utf-8?B?dFRkdHBPNkNNVm5wenVjalB1MnJRajdiNTBMQXRodlRaL0N1RG14YjFndnZn?= =?utf-8?B?NTBIbHFXdlJta0UveFR1S3ZINmk4YThkRVVzWjdxNmNPZmFLVDE2UWlvQU0y?= =?utf-8?B?UWY2UHlaY1MxSXFrUnF2eTlzZTBuay92QVVxYlZ4aUswZHY3NStYSGxZbVdT?= =?utf-8?B?ZGlyM1g4dGYzcWtDTW5VcDczMitxQ3k1aDFYQjJHeG1aMWlnMDZ4elRqZVU4?= =?utf-8?B?VTNhWnhsTmFEY1ZHSWdJSndHajhUMkk1OWhRNlNjcWJLV2E4MXpuZ0I1OVNl?= =?utf-8?B?TlRER3dHalVWZStYbWlzVG5SUHN4RlRNNTMxQnQzV0xSb2NzZ1RwbEdnazJa?= =?utf-8?B?NnAzazgwbXo3dWx5d0x6U0hzR1ppUGZlbTZoWk5uUHM3Um93c1drcEtFbGMw?= =?utf-8?B?S01FclRoS1AvTXNrV0loMC83Ui9vWkQ3c1RLTmQwTUNlZUhwKzhHcmdvSmhQ?= =?utf-8?B?eXBOaEJsdVZNOUZWMURkQUxvK2VCdU5sTkc1bXpHdUpZMjZucjA3SFJTdTVt?= =?utf-8?B?NmExNHdJb2k4cnlwWnFGTVNobE5mdHlTclIrcmFjaVEzRkNGZUQ5VDU3QkUz?= =?utf-8?B?OElKZkNqbnZwRS9FcGxwU2M3c0hZalorOGdnb2t6NEFFalZRSkpxMWtUOStu?= =?utf-8?B?WE10V3Z3SzJpZmUxK2lTZVMyUjNXOE05S0l6cHhQU1BRVXFuQ0JGVE9RTTI0?= =?utf-8?B?eTVveHllazRyTzAydlBmSWdYcnNYK0xUK3gwV2NaUFp4NkRycGN5cXpaK1c2?= =?utf-8?Q?DIOuyCgi0sOE0Gnk=3D?= X-Exchange-RoutingPolicyChecked: Hq6yRYb5pZlreCaP14aU/LxKn+0gpe4FM78m+e2WC9hEpMO1v1giSPVKVe8+CtB9d+3VDAil14TOfGhc3vmYawijKnHg/86Gjoiz98BFn0NnPjqS4/X1cWpIfU7QFN1zjqOx5rFz3Js6j5eosF8AKBG35/wMrn/Jv20iJ9+nQ5h2SrLw51z/UQGIVh69wBDi4IhWZUOoPJtwaOYRvPb4BwjwV6Pquiw2P9DIEk+uPPNuHbEiVyIc99pSF7W7SwvBOK3ZojkctpgQP7/en/NAHav+SWXTMykltTF3LmRqjqpHiCpPonZu/4KrLGn2HJ3B6wIotcWT610izLCTba7+ig== 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: cf5f41aa-194b-45aa-857e-08de94e18eeb X-MS-Exchange-CrossTenant-AuthSource: CH0PR10MB5131.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Apr 2026 20:09:22.0923 (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: /ESnFpU83f6a/77blqWgief9yFS7Z/VTwoQMHQty6YUBTNsaM7dmxASSJGB+BYP7zRuzLTxQIMcTakAFx8tM59ViFZ5P5ZSXjOl5GvW0eVY= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN6PR10MB8022 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-07_04,2026-04-07_05,2025-10-01_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 adultscore=0 mlxscore=0 bulkscore=0 suspectscore=0 malwarescore=0 spamscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2604010000 definitions=main-2604070183 X-Authority-Analysis: v=2.4 cv=MtJiLWae c=1 sm=1 tr=0 ts=69d56476 cx=c_pps a=OOZaFjgC48PWsiFpTAqLcw==:117 a=OOZaFjgC48PWsiFpTAqLcw==:17 a=6eWqkTHjU83fiwn7nKZWdM+Sl24=:19 a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=GoEa3M9JfhUA:10 a=VkNPw1HP01LnGYTKEx00:22 a=jiCTI4zE5U7BLdzWsZGv:22 a=x4eqshVgHu-cdnggieHk:22 a=sdOadaoQDBHrcnOU6LUA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: L-RNzz9yGofeXp71FrfUYyvJh0hQRDUQ X-Proofpoint-ORIG-GUID: L-RNzz9yGofeXp71FrfUYyvJh0hQRDUQ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDA3MDE4MyBTYWx0ZWRfX5gYAplyXjqMm YQNKYq9iegeBsLYLq/3kUjBi153TKj/RH4EBpJPkJDc4TPJC6CeTH7RHn8LmaRITfG8PRXpyA1U qreQcJMCcyQU95zQeRP4J0aovNjBsc+hfpjr9v1WzA8v9H5cOIUDMI/v1pMzWPa8cM8XQMo6Xqu ur/Y130SXjJElEnDlccQ5IudvOFfBY1osFrimZCPn/TKGfSBc4TjB7S5aDImSHb/eJrtDiDlU+u O+Qw45RlJoSY2YcOYucEvnOaPoFA0T6iB/dCR+zZ3cfNBMSu04qhiGioYd4wbQ20pv39etsMb6F bChT8M7RP8XmsBuvPSuwSQJnye2BYin7ej2+Gt126UnuIyYlBW8LKPlKBcCtV7YSLfyAtaPDenY OiVuACSNaMkankRlfseoGVxg0aGOWmgfnlymqWgukYYP+F4hax8X0H90TBl+zLqrFKfIcFZGscQ etcJlSPJc1S4ceGb7cw== X-Rspamd-Queue-Id: B8745180006 X-Stat-Signature: 6h3szktndioaqy8ee9czrs7b3kffr8nr X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1775592574-113377 X-HE-Meta: U2FsdGVkX191NQYjYUS8YwkjzllVi2s0/XMd5V8ykbc1TLwPUp/V+kF6eFiKOhBUKGjhkEEZiP6stF074yaYfd2j4Dv60GBvZdcPry2sgg0eKVWxMxQSOF0OqenoO0GueVWHPrl8vmXf0sMvUqb3zsDZYUUvN+jtQI/t29OgflEBOxD/K22wkOzW/y0PNmQ2xV/dtRa9NRCTmW04K9XET52pBiyJrSr+Gas5BSf2RQbpDQaBudOkIR/j0yjb95U21mgv3yBWv2FB/WZDW6Fh5y2eidvPCZBXc3bqxbVoOCYNrACpYNybToCM7Fb+2T1o+jDqFcvJ33NKxJePJEE5ssDsijAwsfQ7XenQU94/byo1apuZ3H+RJUr29wH60BmFLV9cdVLCtQypdh0dRZjdVjkeRX9whukO3U9oVtwnr+MRuZ5nHhoaXUNAcN9lH1sHLiI9+2R6InvrNdspIpaFts4A50BvP38aHcl0a5eeG03JAjSGUbJps/xi+A/9TDNTWEiZ8m67hLwrB0WmI8Ilc7x/dIO1yfd458lJky5GUDqcEjwsMLzL4kaRVKiM5KLYFnPpCFbiVI1AWQkbUS3Worw2xVf9DXLRT+1/7VH053ZvZ51jZpDQD+Liyb0fNOcAVRL9RDqblhpDocL5c6ptNtAyCyTz+zRMiEMkZjteoBGSFiSLfv3kwtCmWZFj8BnaXnMLP8QkTUcFFhFoFYZOhjO+te2UL/Va6hZORo1aqE5PbmfxmqCEiBax8bPn0WGF4CaemrzeGhrhSCNuNaZ1UtF0TupXPi8K3FaEw3QPD1CJoHMadI2tKaQPyGt9loUSJHRd/7JjQc5WhQUAW1aSF2fnJQcTcsOccQSfIcpJFPU+ZrfMJHXxaEkzKoNd4Z5bnfXHA7lN0EtET4YKbtTuBAGgCl2bpDh9M4MMcwfa5sWqwkaYfezobx/BZ1x6pXTClPunaZ+JzMbLQDYA8Vr o5KxxsLe 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello, I would like to ask for feedback on an MM performance issue triggered by stress-ng's mremap stressor: stress-ng --mremap 8192 --mremap-bytes 4K --timeout 30 --metrics-brief This was first investigated as a possible regression from 0ca0c24e3211 ("mm: store zero pages to be swapped out in a bitmap"), but the current evidence suggests that commit is mostly exposing an older problem for this workload rather than directly causing it. Observed behavior: The metrics below are in this format:     stressor       bogo ops real time  usr time  sys time   bogo ops/s     bogo ops/s                              (secs)    (secs)    (secs)   (real time) (usr+sys time) On a 5.15-based kernel, the workload behaves much worse when swapping is disabled:     swap enabled:       mremap 1660980 31.08 64.78 84.63 53437.09 11116.73     swap disabled:       mremap 40786258 27.94 15.41 15354.79 1459749.43 2653.59 On a 6.12-based kernel with swap enabled, the same high-system-time behavior is also observed:     mremap 77087729 21.50 29.95 30558.08 3584738.22 2520.19 A recent 7.0-rc5-based mainline build still behaves similarly:     mremap 39208813 28.12 12.34 15318.39 1394408.50 2557.53 So this does not appear to be already fixed upstream. The current theory is that 0ca0c24e3211 exposes this specific zero-page-heavy workload.  Before that change, swap-enabled runs actually swapped pages.  After that change, zero pages are stored in the swap bitmap instead, so the workload behaves much more like the swap-disabled case. Perf data supports the idea that the expensive behavior is global LRU lock contention caused by short-lived populate/unmap churn. The dominant stacks on the bad cases include:     vm_mmap_pgoff       __mm_populate         populate_vma_page_range           lru_add_drain             folio_batch_move_lru               folio_lruvec_lock_irqsave                 native_queued_spin_lock_slowpath and:     __x64_sys_munmap       __vm_munmap         ...           release_pages             folios_put_refs               __page_cache_release                 folio_lruvec_relock_irqsave                   native_queued_spin_lock_slowpath It was also found that adding '--mremap-numa' changes the behavior substantially: stress-ng --mremap 8192 --mremap-bytes 4K --timeout 30 --mremap-numa --metrics-brief mremap 2570798 29.39 8.06 106.23 87466.50 22494.74 So it's possible that either actual swapping, or the mbind(..., MPOL_MF_MOVE) path used by '--mremap-numa', removes most of the excessive system time. Does this look like a known MM scalability issue around short-lived MAP_POPULATE / munmap churn? REPRODUCER: The issue is reproducible with stress-ng's mremap stressor: stress-ng --mremap 8192 --mremap-bytes 4K --timeout 30 --metrics-brief On older kernels, the bad behavior is easiest to expose by disabling swap first: swapoff -a stress-ng --mremap 8192 --mremap-bytes 4K --timeout 30 --metrics-brief On kernels with 0ca0c24e3211 ("mm: store zero pages to be swapped out in a bitmap") or newer, the same bad behavior can be seen even with swap enabled, because this zero-page-heavy workload no longer actually swaps pages and behaves much like the swap-disabled case. Typical bad-case behaviour:  - Very large aggregate sys time during a 30s run (for example, ~15000s or higher)  - Poor bogo ops/s measured against usr+sys time (~2500 range in our tests)  - Perf shows time dominated by:       vm_mmap_pgoff -> __mm_populate -> populate_vma_page_range -> lru_add_drain     and       munmap -> release_pages -> __page_cache_release    with heavy time in folio_lruvec_lock_irqsave/native_queued_spin_lock_slowpath Diagnostic variant: stress-ng --mremap 8192 --mremap-bytes 4K --timeout 30 --mremap-numa --metrics-brief That variant greatly reduces the excessive system time, which is one of the clues that the excessive system-time overhead depends on which MM path the workload takes. Thanks in advance! Joe