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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89CE1C432BE for ; Tue, 31 Aug 2021 20:40:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 01F9B61053 for ; Tue, 31 Aug 2021 20:40:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 01F9B61053 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 9B6D26B0074; Tue, 31 Aug 2021 16:40:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9665C940007; Tue, 31 Aug 2021 16:40:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8074A6B0078; Tue, 31 Aug 2021 16:40:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0008.hostedemail.com [216.40.44.8]) by kanga.kvack.org (Postfix) with ESMTP id 7200C6B0074 for ; Tue, 31 Aug 2021 16:40:13 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 1035D8249980 for ; Tue, 31 Aug 2021 20:40:13 +0000 (UTC) X-FDA: 78536543106.27.EC9BA60 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) by imf06.hostedemail.com (Postfix) with ESMTP id 7026F801A89B for ; Tue, 31 Aug 2021 20:40:12 +0000 (UTC) Received: from pps.filterd (m0246627.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 17VIiPD2030606; Tue, 31 Aug 2021 20:40:09 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : content-type : content-id : content-transfer-encoding : mime-version; s=corp-2021-07-09; bh=Y/lQnGg5xfkKSLQttC6uDKpWfWA+mBcgdd5CemvcPOo=; b=ZHF9EUd4X8gYh1okUYCnUil3Vjq2Ygl/hf+CEba54JSKyQKxnK4VL9hsg/qrKfWhFFWM 8574Tccc3mv3a/U/NUCC64EOYmfJXp69ET05uMf9DRg6lqOru81ycnPkzcyk8bukXZUF wJe9IEJX4SbGpgwL2K9hdBLuZ7eBamuKXk0bP7XiudjQE/eiG7mRXTFdBEOYQbk+wROs d8Nn6HVVX2fgCzVwT0oKOhBd/GSXCLQHVWdUytCl3jYwXdb02vBVVUj+vk9DKwjzaal8 OOSvKOK8FNUNceLwWEzcHQRIceTOEXieNFg+Ac4AHE8gmMHClJzPVo61O9Zv5/mAL/f1 CQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : content-type : content-id : content-transfer-encoding : mime-version; s=corp-2020-01-29; bh=Y/lQnGg5xfkKSLQttC6uDKpWfWA+mBcgdd5CemvcPOo=; b=qbq6DF76PM+2AH42UTwwvnaWfz8eW/UmFVrrVBfpHlBjKJX7w6Hga5055TcDVEEouShC n75WSm/CiIlQl/LynLACzMBiCBREJBhI4HtwR80UOFA6+yZi7cimQQ23yrrSLvG5VCv6 ioztOg5H09bvQxtzJvE5kcyYUfZFp4LewgyKq7aXZCCNuZQn7MamZoOuAdinvFbUL2Nc KGdarE4Vej5eAU0yX6DvorcaQMrR8FgmXRKL6T6Uu94tKBzY+LpdzXFid9it0sWvxeJJ FbtMzEpl++U7RBwO5uQY0zpdQ+ls/0cPAWVscxb49xUHdna+oXT6Qk6H5kYA1iklGmqS dw== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by mx0b-00069f02.pphosted.com with ESMTP id 3ase02aehq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Aug 2021 20:40:09 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 17VKZlrh061791; Tue, 31 Aug 2021 20:40:07 GMT Received: from nam11-co1-obe.outbound.protection.outlook.com (mail-co1nam11lp2170.outbound.protection.outlook.com [104.47.56.170]) by aserp3030.oracle.com with ESMTP id 3aqb6ehj8s-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Aug 2021 20:40:07 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=O2VSyeDocLmhg99TtlfPmu/QK0nMgwyaGbK53RObcitcxiipJRUMFcEbtrmHtTFn2+y+q+/VtYUbULJPQfJ87alncKblzuKVNstjhNEqbBgXakD2ecivpF/sXUEKah/wGVnqWFk3T5glPHr3Yg9mklKAR+Zl6AfzN4nguulCZXH3yzPgWSVudlatqAQ/lY+5UlTIUpiSpKSF41lZsov4ItKbG6rHiQlyw3dwiorYp5C7ZBfd7CEhzkX/jpJ1qIXRWvjRBtQYpd/t7tOz+NSiyCDVRR2jBnSijpnFpvgsEf7WMEEdFFF2o6rTM7cLKJ5CL95CSTKY9nan7vowLTDloA== 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-SenderADCheck; bh=Y/lQnGg5xfkKSLQttC6uDKpWfWA+mBcgdd5CemvcPOo=; b=WojIPsksFr8IuPQUQmCzByxMYZViu1l8Njj4KtN1dl8AKGbn3PZZCUBBLd7726zlCtldawCnSJwAgtCiFQn7KUjlzy06Rtttf21iGMewWJC6Wxr2bCS1K09FLqDWhBri0QOrzBZnWAaKfEwHtTNQs0NNKnM6ERWjULNQ6XT9U9TDZwP33s126XvjUjVdpjINOimyx1ZnJ286hzihq2DcJScf6XA775IMB5BSzvqZuFswFQQdv3pVMSWugRS9mnDo8aS9E50NsoViv6Rpj7Ea7UQal7htnk22DGVuKvLtPDmRCYA0ZNPxOwdGh1XMYmUo69SGi34QFS4X5Ax0W5OosA== 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=Y/lQnGg5xfkKSLQttC6uDKpWfWA+mBcgdd5CemvcPOo=; b=h9yXNfPh6psikOla1tFs7ynpj+hYubj3k4Y/gRyVITtksX+UWocQSPuse9PB8Pl/UZ871CwsCYw4iSitDO9jBZMmGkoRLawfWT0ISF3CSYEQF5UMZy2flpIXXNNv8gsAp+n6owUgkZzxIroZahUfM8I4a0jEFTT0xhMAFDTzdqA= Received: from DM6PR10MB4380.namprd10.prod.outlook.com (2603:10b6:5:223::19) by DM5PR1001MB2297.namprd10.prod.outlook.com (2603:10b6:4:31::35) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4457.17; Tue, 31 Aug 2021 20:40:06 +0000 Received: from DM6PR10MB4380.namprd10.prod.outlook.com ([fe80::f4b1:d890:7745:30a3]) by DM6PR10MB4380.namprd10.prod.outlook.com ([fe80::f4b1:d890:7745:30a3%4]) with mapi id 15.20.4457.024; Tue, 31 Aug 2021 20:40:05 +0000 From: Liam Howlett To: "linux-mm@kvack.org" CC: Michel Lespinasse Subject: Strange mmap_lock tracepoint Thread-Topic: Strange mmap_lock tracepoint Thread-Index: AQHXnqhh7VimgmVH/ESa/cE4sY7tPg== Date: Tue, 31 Aug 2021 20:40:05 +0000 Message-ID: <20210831203959.lwofr24z63wjsgkc@revolver> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 3121e7ab-9c51-423c-f85c-08d96cbf840e x-ms-traffictypediagnostic: DM5PR1001MB2297: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:9508; x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0; 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:DM6PR10MB4380.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(7916004)(396003)(366004)(39860400002)(136003)(376002)(346002)(316002)(6486002)(6512007)(8676002)(6916009)(71200400001)(8936002)(9686003)(76116006)(91956017)(86362001)(64756008)(33716001)(83380400001)(1076003)(44832011)(26005)(66446008)(478600001)(38100700002)(5660300002)(122000001)(186003)(66476007)(38070700005)(2906002)(66556008)(4326008)(6506007)(7116003)(66946007);DIR:OUT;SFP:1101; x-ms-exchange-antispam-messagedata-chunkcount: 1 x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?PS6rANa6LdW1iUuM/8otY5peV0lw6istz5dbuvEDyZa2nN93AAAuI+GPZ5Fz?= =?us-ascii?Q?CN5di7oZ7Mv66/QH6fF/JEzAkBOSX8wC48g3NRtGTPR0WGB7gXtbMtDn1cl6?= =?us-ascii?Q?3oa1WIdwcPEv/xSlfE+L7g2fscRoVRFSW75yPNgC3f0MxFk4pSpUFRjWM6+y?= =?us-ascii?Q?xzEpI9pX+3Zb5VI75ZVCve9dHWq9yMGP4zDZuoioJWiNfqA6Hp2BofskbyMj?= =?us-ascii?Q?AE8WuJmeGGGD8zpOz3FD3hIPQ5c0rwLN4hbVmW+FNwhfngoFw6ACKfDtrKfX?= =?us-ascii?Q?tvjUuqg4dbH1eakv+HwRJbeH2snJ/mkHcdGJu9Gc3N29LyIQBqVzJ6ehv7oq?= =?us-ascii?Q?RmKxpsaLpJ++KYVZxIeNYuSOtiEaxFsOi+yCvcAn58SObPQykCsGcde7mqtu?= =?us-ascii?Q?yEFdQ+jEozfCk0zkUNMJNg/K/lueOibeWJ9S3KXrDVMtTyKSE+e4SoiNKTY/?= =?us-ascii?Q?uN4QKDGkDQjcMEhYfkNbc1wam6OegUbhrmO9Asr/WXnKLLS+RJLjXH8fe5Lb?= =?us-ascii?Q?6Op7b52m7FtMhzvckqDTG7sgaSNw9bDf72Rbpg3F4AgrFzVx2tlobrqokwDC?= =?us-ascii?Q?RldGBe7UtLExfq7erFlDU9fS9Wi12Gx9uU/li7iNPltZ2KqdEwCq3Qw0QyQ3?= =?us-ascii?Q?Y1EVUT6W4NBYe2hvV6Dpx6b2SjLKkBR2Gl5iYDkRqPauBHMqJ5oGdHBsceg4?= =?us-ascii?Q?IQHfX03RNOVn010r1OaTHaq0iBgNM4Hm8p+dxPyF3odJpJ/BsvcN7mBivWlT?= =?us-ascii?Q?wKbSAX8Ihs3esz/cK/0EdMIe/bb7v/+Pj9i1CQYpC583K9fyZhMan16/vXXA?= =?us-ascii?Q?Za0MHd+SPoP7amRKx0ArZFOGf/12mbp3RmNSl6oBFyxldDBwRTY5eBItwKvz?= =?us-ascii?Q?DD4apGij+mwoJS+3VUBk1Id6wA8UAj43YlRTTGJG07Y25jrzdarYW/6a02h5?= =?us-ascii?Q?n/nPJWP+5Mj7wZ55b+u3wPPMl4+fkx9l1oZ0bDOwOZ6VBPcTYmCYO9jMinwc?= =?us-ascii?Q?PCaFSaU26ktgLsWZGRQ/jcx7Cgq0xsyLseHaQ6pi9J55Ta/h/lCx6ToEUZh+?= =?us-ascii?Q?nrWICsaheVC0G17U/ian/L2guMWqRlP+nyiG/Y00dr86+TC2E2iz/VBQLfDh?= =?us-ascii?Q?yfeLcJv9+a2QZu/INfQqVkCLfTCOn6QIgN6PzXMns6qCRtILmIB9kY/0HTVO?= =?us-ascii?Q?KsLgo5OxwYC6b5QjlrsQlLLUcZumfi/kmIJGVxaNkTtiNmbZx8AHB9EIDexd?= =?us-ascii?Q?y4V5cF6NVLoDKywoaDFFjMuP90OGLk39eZhvT/0ltouxgtfsX6bxq8uL/KhX?= =?us-ascii?Q?AS1eTIvu4KKKVYo8wYa/tWXK?= x-ms-exchange-transport-forked: True Content-Type: text/plain; charset="us-ascii" Content-ID: <1F130B057D4DD844BE7FAE2104E97A3D@namprd10.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DM6PR10MB4380.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3121e7ab-9c51-423c-f85c-08d96cbf840e X-MS-Exchange-CrossTenant-originalarrivaltime: 31 Aug 2021 20:40:05.9195 (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: fU1biCCIFnEdhiugIb7NkslJAMV+uvc5mL9Sbuiau2qBwlqYCIyJqtRG2hLD9Z6pU3SvlpQZlxLHe0y8ThwXFg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR1001MB2297 X-Proofpoint-Virus-Version: vendor=nai engine=6300 definitions=10093 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 phishscore=0 suspectscore=0 adultscore=0 mlxscore=0 mlxlogscore=631 malwarescore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108310111 X-Proofpoint-GUID: gwEPqFDRiOxDdV0H63IWxLcfOhhHXhov X-Proofpoint-ORIG-GUID: gwEPqFDRiOxDdV0H63IWxLcfOhhHXhov Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=ZHF9EUd4; dkim=pass header.d=oracle.com header.s=corp-2020-01-29 header.b=qbq6DF76; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=h9yXNfPh; spf=none (imf06.hostedemail.com: domain of liam.howlett@oracle.com has no SPF policy when checking 205.220.165.32) smtp.mailfrom=liam.howlett@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Stat-Signature: 6k3xwyykpfwsfbjmkixntqz8cuqtb9qw X-Rspamd-Queue-Id: 7026F801A89B X-Rspamd-Server: rspam04 X-HE-Tag: 1630442412-452596 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000209, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello, I've been trying to trace the mmap_lock calls using tracepoints and captured this behaviour which I cannot explain. This was with the maple tree v2 patches running ebizzy with multiple threads in an x86_64 KVM using 8 virtual CPUs. AFAICT, there are zero callers that use the mmap_lock directly besides a prefetchw(&mm->mmap_lock); ebizzy-803 [000] .... 5376.655366: lock_release: 00000000de8= cf25e lock ebizzy-803 [000] .... 5376.655366: lock_release: 00000000b5e= 38448 ptlock_ptr(page) ebizzy-803 [000] .... 5376.655367: lock_release: 000000006b5= 81afd &mm->mmap_lock ebizzy-803 [000] .... 5376.655367: mmap_lock_released: mm=3D= 000000001de7b122 memcg_path=3D write=3Dfalse =20 ebizzy-803 [000] .... 5376.655369: mmap_lock_start_locking: = mm=3D000000001de7b122 memcg_path=3D write=3Dfalse =20 ebizzy-803 [000] .... 5376.655369: mmap_lock_acquire_returne= d: mm=3D000000001de7b122 memcg_path=3D write=3Dfalse success=3Dfalse =20 ebizzy-803 [000] .... 5376.655369: mmap_lock_start_locking: = mm=3D000000001de7b122 memcg_path=3D write=3Dfalse =20 ebizzy-803 [000] .... 5376.655369: lock_acquire: 000000006b5= 81afd read &mm->mmap_lock ebizzy-803 [000] d... 5376.655369: lock_acquire: 00000000984= d533e &sem->wait_lock ebizzy-803 [000] d... 5376.655370: lock_release: 00000000984= d533e &sem->wait_lock ebizzy-803 [000] d... 5376.655370: lock_acquire: 00000000cbb= 1a456 &rq->__lock ebizzy-803 [000] d... 5376.655371: lock_acquire: 00000000b3d= 53a93 read rcu_read_lock ebizzy-803 [000] d... 5376.655371: lock_release: 00000000b3d= 53a93 rcu_read_lock ebizzy-803 [000] d... 5376.655371: lock_acquire: 00000000b3d= 53a93 read rcu_read_lock ebizzy-803 [000] d... 5376.655371: lock_release: 00000000b3d= 53a93 rcu_read_lock ebizzy-803 [000] d... 5376.655372: lock_acquire: 00000000b3d= 53a93 read rcu_read_lock ebizzy-803 [000] d... 5376.655372: lock_release: 00000000b3d= 53a93 rcu_read_lock ebizzy-803 [000] d... 5376.655372: lock_release: 00000000cbb= 1a456 &rq->__lock -0 [000] d... 5376.655373: lock_acquire: 00000000cbb= 1a456 &rq->__lock -0 [000] d... 5376.655373: lock_release: 00000000cbb= 1a456 &rq->__lock -0 [000] d... 5376.655373: lock_acquire: 00000000bb7= b405b read tk_core.seq.seqcount -0 [000] d... 5376.655374: lock_release: 00000000bb7= b405b tk_core.seq.seqcount -0 [000] d... 5376.655374: lock_acquire: 000000007c3= ac380 read jiffies_seq.seqcount -0 [000] d... 5376.655374: lock_release: 000000007c3= ac380 jiffies_seq.seqcount -0 [000] d.h. 5376.655460: lock_acquire: 00000000bb7= b405b read tk_core.seq.seqcount -0 [000] d.h. 5376.655460: lock_release: 00000000bb7= b405b tk_core.seq.seqcount -0 [000] d.h. 5376.655460: lock_acquire: 00000000f7c= 85b8f hrtimer_bases.lock -0 [000] d.h. 5376.655461: lock_acquire: 00000000bb7= b405b read tk_core.seq.seqcount -0 [000] d.h. 5376.655461: lock_release: 00000000bb7= b405b tk_core.seq.seqcount -0 [000] d.h. 5376.655461: lock_release: 00000000f7c= 85b8f hrtimer_bases.lock -0 [000] d.h. 5376.655462: lock_acquire: 00000000bb7= b405b read tk_core.seq.seqcount -0 [000] d.h. 5376.655462: lock_release: 00000000bb7= b405b tk_core.seq.seqcount -0 [000] d.h. 5376.655462: lock_acquire: 00000000cbb= 1a456 &rq->__lock -0 [000] d.h. 5376.655463: lock_release: 00000000cbb= 1a456 &rq->__lock -0 [000] d.h. 5376.655463: lock_acquire: 00000000f7c= 85b8f hrtimer_bases.lock -0 [000] d.h. 5376.655464: lock_release: 00000000f7c= 85b8f hrtimer_bases.lock -0 [000] d.h. 5376.655464: lock_acquire: 00000000bb7= b405b read tk_core.seq.seqcount -0 [000] d.h. 5376.655464: lock_release: 00000000bb7= b405b tk_core.seq.seqcount -0 [000] d... 5376.655466: lock_acquire: 00000000bb7= b405b read tk_core.seq.seqcount -0 [000] d... 5376.655466: lock_release: 00000000bb7= b405b tk_core.seq.seqcount -0 [000] d... 5376.655467: lock_acquire: 000000007c3= ac380 read jiffies_seq.seqcount -0 [000] d... 5376.655467: lock_release: 000000007c3= ac380 jiffies_seq.seqcount -0 [000] d.h. 5376.655488: lock_acquire: 00000000bb7= b405b read tk_core.seq.seqcount -0 [000] d.h. 5376.655489: lock_release: 00000000bb7= b405b tk_core.seq.seqcount -0 [000] d.h. 5376.655489: lock_acquire: 00000000cbb= 1a456 &rq->__lock -0 [000] dNh. 5376.655490: lock_release: 00000000cbb= 1a456 &rq->__lock -0 [000] dN.. 5376.655490: lock_acquire: 00000000cbb= 1a456 &rq->__lock -0 [000] d... 5376.655491: lock_release: 00000000cbb= 1a456 &rq->__lock ebizzy-803 [000] d... 5376.655491: lock_acquire: 00000000cbb= 1a456 &rq->__lock ebizzy-803 [000] d... 5376.655492: lock_release: 00000000cbb= 1a456 &rq->__lock ebizzy-803 [000] .... 5376.655492: mmap_lock_acquire_returne= d: mm=3D000000001de7b122 memcg_path=3D write=3Dfalse success=3Dtrue The following tracepoints were enabled: events/mmap_lock/enable events/lock/enable My reading of the above trace is that the ebizzy thread dropped the lock and immediately attempted to reacquire and detected it was in contention so the thread added itself to the list and went to sleep only to wake up and get the lock? Doesn't that mean the mmap_lock is _not_ contended? The lack of contention makes sense since there is no tracepoint of an attempt to acquire the lock between the dropping of the lock and the same MM waking up to get the lock. What is even stranger is if I change the value of _Q_PENDING_LOOPS from (1 << 9) to (1 << 10), the benchmark performs better. >From the above trace and the effects of the _Q_PENDING_LOOPS change, it looks like the lock is somehow remaining in a state that causes a failure to acquire the lock even when it is not held or contended? Thanks, Liam=