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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6B1B3C4828D for ; Mon, 5 Feb 2024 08:40:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B5B7B6B0075; Mon, 5 Feb 2024 03:40:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B0B546B0078; Mon, 5 Feb 2024 03:40:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8EA328D0001; Mon, 5 Feb 2024 03:40:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 7794F6B0075 for ; Mon, 5 Feb 2024 03:40:43 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 220DD16045B for ; Mon, 5 Feb 2024 08:40:43 +0000 (UTC) X-FDA: 81757104366.06.9312D7F Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.13]) by imf14.hostedemail.com (Postfix) with ESMTP id D6008100016 for ; Mon, 5 Feb 2024 08:40:38 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=dZdEYsr3; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}"); spf=pass (imf14.hostedemail.com: domain of fengwei.yin@intel.com designates 198.175.65.13 as permitted sender) smtp.mailfrom=fengwei.yin@intel.com; dmarc=pass (policy=none) header.from=intel.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1707122439; 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:in-reply-to:references:references:dkim-signature; bh=DpXTXI7OrymtECuLxZA2c+pygWNMpTk1V17X3kSqP/g=; b=mqZuS4wGQkOiAr7Q9SgiJ4BCMbiswqiTedYIRjERJ2GUaPCo1VZtsHq8vHrS/dOFQ6+JjS EzdpkIOCnGB3H962GiVq8oeDJl/EsXZAWT4uWq5Oafz6rhVeCLGIe3qPouDniGK5OXTi3v z0gziV/dhK/rYSpR7152ok8wJsLlDJQ= ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1707122439; a=rsa-sha256; cv=fail; b=MxMN9IJIfrRXPmvnATWiYSdVVIis9MlNwT/fw6BefLSHx8ddD1iVoAbhmGlqYeBw+HQfiI E5fyAnz21F5f1Yv/y1SqTnY+J60FX8PSBvyLDsbU5MbQqvrnVNqKlOP+T5TEDf0Kwv2MII ZtiawszdYLwLjjWpa7C5QKld1Z3dOsM= ARC-Authentication-Results: i=2; imf14.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=dZdEYsr3; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}"); spf=pass (imf14.hostedemail.com: domain of fengwei.yin@intel.com designates 198.175.65.13 as permitted sender) smtp.mailfrom=fengwei.yin@intel.com; dmarc=pass (policy=none) header.from=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1707122439; x=1738658439; h=message-id:date:subject:to:cc:references:from: in-reply-to:content-transfer-encoding:mime-version; bh=ERXOABV27wEIRZD1aIdUBNuhGKhAUzN3ii/AaDe0AJ0=; b=dZdEYsr31xhuCdjMuHpOqcNFozuy6GZLrtGom5HFtn+U7GpKihRVPYxH qfW+s4V9lSQFN6d0s1FxbRPAoemNUFmlsioqLSmo3Gp7OEBQXd35kASkh 6nc7ngGyJxpjxHwMVPMFp64U7gb5ERGgcEsfcTGYGkwOY27uhqpQezIjR RmmNlD9ckG3JIM9YN9I/oFdyInaNqSiYOWeiJLdDFxHG7H0kyHvJZzygy OXADQRabPSZbvUkhPc+Fzeg1upjRGNShSWb9kR0Km9VL8RBuhIWFNR1J3 eWrzavxHwG0MJ+rYu9aZTywZ7BvOZyi6Ut1turYvFBjfEh4/At5l5eOnk A==; X-IronPort-AV: E=McAfee;i="6600,9927,10974"; a="11569731" X-IronPort-AV: E=Sophos;i="6.05,242,1701158400"; d="scan'208";a="11569731" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Feb 2024 00:40:37 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.05,242,1701158400"; d="scan'208";a="657541" Received: from fmsmsx601.amr.corp.intel.com ([10.18.126.81]) by orviesa010.jf.intel.com with ESMTP/TLS/AES256-GCM-SHA384; 05 Feb 2024 00:40:37 -0800 Received: from fmsmsx601.amr.corp.intel.com (10.18.126.81) by fmsmsx601.amr.corp.intel.com (10.18.126.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Mon, 5 Feb 2024 00:40:36 -0800 Received: from fmsedg601.ED.cps.intel.com (10.1.192.135) by fmsmsx601.amr.corp.intel.com (10.18.126.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35 via Frontend Transport; Mon, 5 Feb 2024 00:40:36 -0800 Received: from NAM12-DM6-obe.outbound.protection.outlook.com (104.47.59.168) by edgegateway.intel.com (192.55.55.70) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Mon, 5 Feb 2024 00:40:36 -0800 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=e/w0koRdBzdIMwGZ9Ngo5XCsMa0Gb02TSaHpx9vxF842V7eKkOqaphe/ae8MTWVmfkZMp0iCZz3ntaozQ6b2AMWZe/H4m5uiX3xvBJhXTBMnxLfOlHSVrCju1VdGBrEl4qiOgDyavim2w9ssXnRpB2VXPL7r2zXFzjaO3LjPOq9INrghDwkunEB0rnUVW1Pq3vw0TuqKfXpXv1GoyR22PE7+JJ6NoD/FjuLYZt+aEENhgtAvww1Vmq6Uo0IB2XKXqbKe/pzFEJfy7FCdNQh9c3c1WABCE2D67pBoC1k0oLZYFr0+dHPs3PIrJCo7Aw9OTsCStk8tJeTImUq9pLVuSA== 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=DpXTXI7OrymtECuLxZA2c+pygWNMpTk1V17X3kSqP/g=; b=i80X5INsSKxo1n1VApaNpa8twIEZGpdM3joP+R8veydaQqsGtwf6LnQIEKR3RRv+rwKAvmQrpEHmfV7Xm8Qbic0tvRefVzsCVDCXu3eXYAAKddHHZA7YZ+hSoYyGPoWyUL3mkYTMsjk/SAm+Sxn8nbv178xfPGFMoZxroT3GB2HKoXLr/cm6ZfgDQ/4YvUcvc8tE13ILOfVGrNt8sZC1gqQpzE1Sq1n6IDDcPkx3kW4uy7WLEhSOa6ZZXlb8RCYS/AbdtqLOfeVBWwDCiXWvbyAQxhfTmt6hZSNwohOzLZlyLWCDVtNfdWNpaqvYfvAlrAEVkRqCv52GFoT9a+Mphg== 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 Received: from CO1PR11MB4820.namprd11.prod.outlook.com (2603:10b6:303:6f::8) by CO6PR11MB5569.namprd11.prod.outlook.com (2603:10b6:303:139::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7249.33; Mon, 5 Feb 2024 08:40:34 +0000 Received: from CO1PR11MB4820.namprd11.prod.outlook.com ([fe80::4647:3802:133d:8fc]) by CO1PR11MB4820.namprd11.prod.outlook.com ([fe80::4647:3802:133d:8fc%6]) with mapi id 15.20.7249.032; Mon, 5 Feb 2024 08:40:34 +0000 Message-ID: <07e5ee4d-e0b7-4799-80a1-cccfbab2dd4d@intel.com> Date: Mon, 5 Feb 2024 16:40:27 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] filemap: avoid unnecessary major faults in filemap_fault() Content-Language: en-US To: "zhangpeng (AS)" , David Hildenbrand , "Huang, Ying" CC: , , , , , , , References: <20240204093526.212636-1-zhangpeng362@huawei.com> <87zfwf39ha.fsf@yhuang6-desk2.ccr.corp.intel.com> <85e03dd9-8bd7-d516-ebe4-84dd449a9fb2@huawei.com> <87mssf2yiv.fsf@yhuang6-desk2.ccr.corp.intel.com> <25de8872-ad79-e5e6-054c-9ac5e7191416@huawei.com> <1a967b8d-7218-4d3f-9dd2-ae1c66f626c7@redhat.com> From: Yin Fengwei In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SG2PR02CA0082.apcprd02.prod.outlook.com (2603:1096:4:90::22) To CO1PR11MB4820.namprd11.prod.outlook.com (2603:10b6:303:6f::8) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PR11MB4820:EE_|CO6PR11MB5569:EE_ X-MS-Office365-Filtering-Correlation-Id: 2bb5e78c-7a3a-4d60-f61f-08dc26261e50 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr 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:CO1PR11MB4820.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230031)(376002)(39860400002)(136003)(366004)(396003)(346002)(230922051799003)(451199024)(186009)(64100799003)(1800799012)(2616005)(26005)(41300700001)(31686004)(966005)(6486002)(36756003)(6512007)(478600001)(6666004)(83380400001)(6506007)(82960400001)(38100700002)(53546011)(6636002)(66556008)(4326008)(2906002)(5660300002)(110136005)(66946007)(66476007)(31696002)(86362001)(7416002)(316002)(8936002)(8676002)(43740500002)(45980500001);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?UVk5bkRjL1lyY3g0akhPSk1rcDFtdFV6RzBrVjltdWpuNHJTbDVRdzdEZGZO?= =?utf-8?B?OSttS2V0Z0ZBamU4QVkrZ0ZtZmU3ZTFOY1FXd0ZxZ3c0Vko0WHA3OVVqQ1Nn?= =?utf-8?B?ZkZwWTc1bldHbEMwVDFhS0F2ZHpVeDVlc0FLcGhqQWpQT21CeUV2RVc0b3NZ?= =?utf-8?B?WFBrcXh1aHQvK0hiaFpWSHRNMXhGTDNHaEdhZ3dPUElVZjFxQ1ZQUXdlUXEv?= =?utf-8?B?bWN2RHo0TXBFL0JRQjd0ZS82dEFVRk5BTnZaOC9FQ3Vld2NHemk0L3Joa2k5?= =?utf-8?B?dXJianBKM3N4TGx6UmRpaTcrRVJsTGtLa0ludVNsVFY1NFB2aW9KZ2RZM3Jy?= =?utf-8?B?allvSjUzVFJBWCt3Ry83V3F0S3BnVFZKS01ySFRvMmVxQVdvT01lNUljNHZs?= =?utf-8?B?cVAyZDZoZ1g0TmlOZWFLWlJKU3Eza2txUjc3T1hPMitpdDlIRTJqZmNyNjdw?= =?utf-8?B?U2wzaWhCSkRpQmdRMDRPNStOS1RyaDNFbHh1OUlnMnJqNXVDQmRHUUJBZmF0?= =?utf-8?B?bmptWldPRGp5U3IxOVhnREdvZU5lakcxVkVML0lZcElSYWVxSDBpRURqbVN4?= =?utf-8?B?RTdMbmplZjRyd09iSGN6cnJzTllicWZadUs2dUoxaVFyN3JrL3FyS2FwOEMx?= =?utf-8?B?Z0lJRjlVUm9QQmNGY1hHNDgrT1BuUTFOMG4vRHdmWjN6d0djY1NoMURPMzlx?= =?utf-8?B?b3FFYktMMExTTUY0eXA2SUpJNzNVbnN0QldBaDFaNFc3czFrejQwZEhVZXl3?= =?utf-8?B?ZDZGOHcrakJvRzY4MzVhR0RPdEdqSlc4blRjeEJPUXgwNFdnZEViODh2a0sx?= =?utf-8?B?dDg1bnVWU0FsZ0FqM0xicUdJUlNuZnhmTkdFV3hNRnRYdnpVeFA1S0ZWY0Na?= =?utf-8?B?MEVIbCsxUm9jQ0xPcytiZ1VaTElSVkxqbXRIeWNrQ2luUXowMFpWUjMzL2FG?= =?utf-8?B?YVZuQnA2MmkzQlp1ajF1S016RFVkbzhjWGFiNks1Mlo1OUdjdEJBM3FQMmFG?= =?utf-8?B?ZmJRV01YMmhzVVd3Q2xDcHlqWVBnNDVTdURrT0p4cStsQU9VTzNlMFNBYkVy?= =?utf-8?B?R1BudHp5T0dEbXBLRHFCRHgxQk96dzl2NXMxVXNJUnEyMTdRcEdRd3JPZDBk?= =?utf-8?B?Z3pLcHl4eEdja0F4TmRxeGdpbi80VEF4bVRYT2N3Qk4xTTUyOTRWM3FMd1NB?= =?utf-8?B?TmZmaEpBQVdtNkJxa2gvS2wwbE1la1RUTk92WG1VRnZESnNMTkdFYmlvWXBL?= =?utf-8?B?ZmpNS2NUUmk0WmFmQjd1NFFMMDdRbHBPckpHS3FIUTZkUGNTLzhTeU5KOGVv?= =?utf-8?B?WGJseHhISlBJRFZqMm5Nd2lzcjZacVhNTm1OSytRSjVnWTV3WGU5V3cwZGFP?= =?utf-8?B?S2tJU2tNdXlEKy9CY084VHRNM2hKaU5aSmg0Wi92ZVhpaEV5U0ZQNGwxLzVi?= =?utf-8?B?UGNKK1hhV2oyUVRjc0x2RHMwdngvWEh6TkpZSDNjaUU1MFA3QllKaFpKNklV?= =?utf-8?B?N1hucUtaK0dqK2xZWkFpVGo1dCtHTzFFOXQ3ZHBPb0VoWGJQUVNTWGZ0R3BC?= =?utf-8?B?R3BwY3ZGemRUTDU5VmtZV0RXSHRiM0poU01uUlBCN1RJYzA4TnNVbkMrbzVn?= =?utf-8?B?RDNGYmZLaXJXQzM5QUZWc25MNU1taFVkWHo5REE1ZDgzRVhCMm93b285UFNR?= =?utf-8?B?VjJhbHVRek10UUJDSVUyd1FZeFVrQm5wa2Y1Vll5Q0o5WlljSW9PMGhvTkJa?= =?utf-8?B?emsvcElVMjJUMEVrTm1HZ2Y3dW83dFFuZkpEdEFpWERFa3h6QTFHckVUYUll?= =?utf-8?B?bE9DUGNaMHZXSW8wVUI2T3c3aWNNbjFjSnFRU1pKYkFUMGFrSWwzWGQrSHZU?= =?utf-8?B?dVhoZW9mUEF5bzkzTGJCb093bmlGY201VW9ZdC9lc1I0V2dJNkZuUzJFVWR3?= =?utf-8?B?QllSQ3N5ZVpoWEdUZHJteU02R3RTRVh6V2NSa2pMVm9Wdk5XUGlSMmpHTmxQ?= =?utf-8?B?eldaZVJlLzZaMzJjQVlDS2xPSVJOd0lsSHZFTTRNbkMxQTl3eEpBY1FicE4r?= =?utf-8?B?c0hBQWlReXQ5eUpxaVJEVVppV1RFN2NYUHRhM3NnS2V1UUhVOXB3MkV1N2lI?= =?utf-8?B?TTgxMUNMZmZrVys0VnRLcjJibSsxYVduVlJmVzd4dmx5ZThadTQ1TUIxZGVE?= =?utf-8?B?TlE9PQ==?= X-MS-Exchange-CrossTenant-Network-Message-Id: 2bb5e78c-7a3a-4d60-f61f-08dc26261e50 X-MS-Exchange-CrossTenant-AuthSource: CO1PR11MB4820.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Feb 2024 08:40:34.2357 (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: PUqVugpe6uHMDaligyT9qPQCjQvQiuQwuQz+f4L2NNUQSzEUuWvVc/EO/vWtJtuSbj/4cNWySk6iBDgecyTLGA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CO6PR11MB5569 X-OriginatorOrg: intel.com X-Stat-Signature: a11s58c1yyyfmmcor45oz9tubnjy5g46 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D6008100016 X-Rspam-User: X-HE-Tag: 1707122438-707212 X-HE-Meta: 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 vLxz++qE Bxc9k8EiyywBEli6gIyss0cBHWLsCKgSfZHul9sL/HZXa2sFYTUzaIlmucT/RhBxoDW23j+TlOKuaCK7HUnF6j7wNs1ktXCIdIYotAi5eedHpmc6OC1i534Lm/dfxH8paFCZ+E+uzdE97F3IA0sOlWqw/bxXE/xIcUSXhB2TtOP9+EwmGOYZDsEM2+96NF7OeQfdN/MWMXJJfhFRceH5mt/+YMWMRNXIcxI283HqTpkmCe9DxUULGzgo33+XeXDhwLuVHse+2xAISV8Y63g2/K31ej2n73xHrmZFOIJ9vEJhYPdYwVOEnO2DFhdki2b3yrW6dkS0dnqaCTtA9K7TDSRurvb1jBYGh7mhlzfo1nhqMx6RQagZdM6/Yevjj5F6GemEH+RQqcexTtDwWrThCbWmszfqAADqDr54FVTIhmG+93q9Bzi7RKZzEAxbf+Z4m8bNVYPYXzCYmlSbSjZoCpxbVGXHu85swLUZAnYLtYQM4ot8FrHKoHAgpWpasMpeXpSbsFOI/Vm2YBXWdGPDBjTSmXMOGVIJ1Rhyi X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/5/24 15:36, zhangpeng (AS) wrote: > On 2024/2/5 15:31, David Hildenbrand wrote: > >> On 05.02.24 08:24, zhangpeng (AS) wrote: >>> On 2024/2/5 14:52, Huang, Ying wrote: >>> >>>> "zhangpeng (AS)" writes: >>>>> On 2024/2/5 10:56, Huang, Ying wrote: >>>>>> Peng Zhang writes: >>>>>>> From: ZhangPeng >>>>>>> >>>>>>> The major fault occurred when using mlockall(MCL_CURRENT | MCL_FUTURE) >>>>>>> in application, which leading to an unexpected performance issue[1]. >>>>>>> >>>>>>> This caused by temporarily cleared PTE during a read/modify/write update >>>>>>> of the PTE, eg, do_numa_page()/change_pte_range(). >>>>>>> >>>>>>> For the data segment of the user-mode program, the global variable area >>>>>>> is a private mapping. After the pagecache is loaded, the private anonymous >>>>>>> page is generated after the COW is triggered. Mlockall can lock COW pages >>>>>>> (anonymous pages), but the original file pages cannot be locked and may >>>>>>> be reclaimed. If the global variable (private anon page) is accessed when >>>>>>> vmf->pte is zeroed in numa fault, a file page fault will be triggered. >>>>>>> >>>>>>> At this time, the original private file page may have been reclaimed. >>>>>>> If the page cache is not available at this time, a major fault will be >>>>>>> triggered and the file will be read, causing additional overhead. >>>>>>> >>>>>>> Fix this by rechecking the PTE without acquiring PTL in filemap_fault() >>>>>>> before triggering a major fault. >>>>>>> >>>>>>> Testing file anonymous page read and write page fault performance in ext4 >>>>>>> and ramdisk using will-it-scale[2] on a x86 physical machine. The data >>>>>>> is the average change compared with the mainline after the patch is >>>>>>> applied. The test results are within the range of fluctuation, and there >>>>>>> is no obvious difference. The test results are as follows: >>>>>>>             processes processes_idle threads threads_idle >>>>>>> ext4 file write:    -1.14%    -0.08%         -1.87% 0.13% >>>>>>> ext4 file read:         0.03%      -0.65% -0.51%    -0.08% >>>>>>> ramdisk file write:    -1.21%    -0.21%         -1.12% 0.11% >>>>>>> ramdisk file read:     0.00%    -0.68%         -0.33% -0.02% >>>>>>> >>>>>>> [1] https://lore.kernel.org/linux-mm/9e62fd9a-bee0-52bf-50a7-498fa17434ee@huawei.com/ >>>>>>> [2] https://github.com/antonblanchard/will-it-scale/ >>>>>>> >>>>>>> Suggested-by: "Huang, Ying" >>>>>>> Suggested-by: Yin Fengwei >>>>>>> Signed-off-by: ZhangPeng >>>>>>> Signed-off-by: Kefeng Wang >>>>>>> --- >>>>>>> RFC->v1: >>>>>>> - Add error handling when ptep == NULL per Huang, Ying and Matthew Wilcox >>>>>>> - Check the PTE without acquiring PTL in filemap_fault(), suggested by >>>>>>>      Huang, Ying and Yin Fengwei >>>>>>> - Add pmd_none() check before PTE map >>>>>>> - Update commit message and add performance test information >>>>>>> >>>>>>>     mm/filemap.c | 18 ++++++++++++++++++ >>>>>>>     1 file changed, 18 insertions(+) >>>>>>> >>>>>>> diff --git a/mm/filemap.c b/mm/filemap.c >>>>>>> index 142864338ca4..b29cdeb6a03b 100644 >>>>>>> --- a/mm/filemap.c >>>>>>> +++ b/mm/filemap.c >>>>>>> @@ -3238,6 +3238,24 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) >>>>>>>                 mapping_locked = true; >>>>>>>             } >>>>>>>         } else { >>>>>>> +        if (!pmd_none(*vmf->pmd)) { >>>>>>> +            pte_t *ptep; >>>>>>> + >>>>>>> +            ptep = pte_offset_map_nolock(vmf->vma->vm_mm, vmf->pmd, >>>>>>> +                             vmf->address, &vmf->ptl); >>>>>>> +            if (unlikely(!ptep)) >>>>>>> +                return VM_FAULT_NOPAGE; >>>>>>> +            /* >>>>>>> +             * Recheck pte as the pte can be cleared temporarily >>>>>>> +             * during a read/modify/write update. >>>>>>> +             */ >>>>>> I think that we should add some comments here about the racy checking. >>>>> I'll add comments in a v2 as follows: >>>>> /* >>>>>    * Recheck PTE as the PTE can be cleared temporarily >>>>>    * during a read/modify/write update of the PTE, eg, >>>>>    * do_numa_page()/change_pte_range(). This will trigger >>>>>    * a major fault, even if we use mlockall, which may >>>>>    * affect performance. >>>>>    */ >>>> Sorry, my previous words aren't clear enough.  I mean some comments as >>>> follows, >>>> >>>> We don't hold PTL here, so the check is still racy.  But acquiring PTL >>>> hurts performance and the race window seems small enough. >>> >>> Got it. I'll add comments in a v2 as follows: >>> /* >>>    * Recheck PTE as the PTE can be cleared temporarily >>>    * during a read/modify/write update of the PTE. >>>    * We don't hold PTL here as acquiring PTL hurts >>>    * performance. So the check is still racy, but >>>    * the race window seems small enough. >>>    */ >> >> It'd be worth spelling out what happens when we lose the race. >> > I'll add what happens when we lose the race as follows: > /* >  * Recheck PTE as the PTE can be cleared temporarily >  * during a read/modify/write update of the PTE, eg, >  * do_numa_page()/change_pte_range(). This will trigger >  * a major fault, even if we use mlockall, which may >  * affect performance. >  * We don't hold PTL here as acquiring PTL hurts >  * performance. So the check is still racy, but >  * the race window seems small enough. >  */ > I believe David was asking to add: "...but the race window seems small enough. If we lose the race during the check, the page_fault will be triggered. Butthe page table entry lock still make sure the correctness: - If the page cache is not reclaimed, the page_fault will work like the page fault was served already and bail out. - If the page cache is reclaimed, the major fault will be triggered, page cache is filled, page_fault also work like the page fault was served already and bail out. "