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 B0F0BC38145 for ; Thu, 8 Sep 2022 01:55:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 35ACF8D0002; Wed, 7 Sep 2022 21:55:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2E27B6B0073; Wed, 7 Sep 2022 21:55:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 135AD8D0002; Wed, 7 Sep 2022 21:55:42 -0400 (EDT) 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 017E96B0072 for ; Wed, 7 Sep 2022 21:55:41 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id BC048A211E for ; Thu, 8 Sep 2022 01:55:41 +0000 (UTC) X-FDA: 79887251682.01.125BE20 Received: from NAM04-DM6-obe.outbound.protection.outlook.com (mail-dm6nam04on2046.outbound.protection.outlook.com [40.107.102.46]) by imf17.hostedemail.com (Postfix) with ESMTP id 0B83240076 for ; Thu, 8 Sep 2022 01:55:40 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=ZSnTPbqAumrsYtkpR/kPgySTzqGYYsN7GlKG1bxPT3rvqL/5Ek1EHk6qzebL+O0z3Ok8zNp0qTE2wex3FxqYPaaMAExMY5/G8Ah/xG7hpEGUIa8ss0Lx+wDHOS0EqzUyrR9P7r6tufMOZI2HUo6xy6KtZOSuef4aFQzpDb8HRN2oBvID2T7XIxRK/zUDaZ6Eela/oCjUiiwmrxVplyWrQRteeKKLBjTRPIcphBLkNk6prNyHah+kjDMN3Uqur8c9VrIFy+DkwdvuoYUIs5Hg338nsV3gIbcgo6w0YCmg6ZPBkoieU4vlO7ExE6ZAmYUmxkSNRSUx4I0ICyiDxJiDDA== 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=hq/bpeg8tDWKR+NcspZOy+u7n2WvOpQMEGj1oAkqrO4=; b=kkDZt1QmTD7fpRarZenXoOlEjnUNUziuDdFXZhGe0LdpcdykQykPM3RAb/OWq1ic2+dw2TGRtlzRJOjGyQQcyTL0w3pIhxjxs2aFn/GC76Awv/yinAlrJjBM5+MqbsUOcAxi3S+DCHxUO/rPwd55q8kl64UtG6dAf1CRC3VHbSwH78rJ8DJvemVNiGN7Lx9CfbogDFYBF+7IIUWnhQ0oHegcDRC2SqplETEptApR43zThM3rD2cDFFVtJNNqO6p2TYq54EWzl2MNmlxdh2jmnb2m/idbYnuqI3wTvmn/eIW6nIfHxNvZcINYMsdVZH2cjjKrisjCo5QOrP8IWYxBdw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 12.22.5.238) smtp.rcpttodomain=vger.kernel.org smtp.mailfrom=nvidia.com; dmarc=pass (p=reject sp=reject pct=100) action=none header.from=nvidia.com; dkim=none (message not signed); arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=hq/bpeg8tDWKR+NcspZOy+u7n2WvOpQMEGj1oAkqrO4=; b=P8GkI94X//sIWvYqaa6Rv3vOLtryQhD0PgsIqyj7dJTAKFF73qrYK9A0Y96z/lv8N4djgsp1y9mm5ZfFbBcyvOM1RwyOlvawQYw9Hk1fBJfBg0bwJ8+h/D1Pn8uwtZaZSGKPZFgbUpMcbzZLgs5Jo3/lL/QFmnQS8Ajmj/jq7OUG0H7sXYs2AfGu3l7npQOA8HaZ+QD2IZD420fnzEFKPtVBsSuCR3jlwJjUG2xMSE2mGcYX/GH9uV/8h2zeejzDwQckQNnbbYREi6tfwzJuEjEBj9YtsOJELTTj0lg2MdP3zu0GrDcuEVnBD1kfvECjrsleS1Ec5nhwLSVWy08QlQ== Received: from MW4PR03CA0220.namprd03.prod.outlook.com (2603:10b6:303:b9::15) by CY5PR12MB6300.namprd12.prod.outlook.com (2603:10b6:930:f::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5588.14; Thu, 8 Sep 2022 01:55:38 +0000 Received: from CO1NAM11FT012.eop-nam11.prod.protection.outlook.com (2603:10b6:303:b9:cafe::50) by MW4PR03CA0220.outlook.office365.com (2603:10b6:303:b9::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5588.13 via Frontend Transport; Thu, 8 Sep 2022 01:55:38 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 12.22.5.238) smtp.mailfrom=nvidia.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=nvidia.com; Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates 12.22.5.238 as permitted sender) receiver=protection.outlook.com; client-ip=12.22.5.238; helo=mail.nvidia.com; pr=C Received: from mail.nvidia.com (12.22.5.238) by CO1NAM11FT012.mail.protection.outlook.com (10.13.175.192) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.20.5612.13 via Frontend Transport; Thu, 8 Sep 2022 01:55:38 +0000 Received: from rnnvmail201.nvidia.com (10.129.68.8) by DRHQMAIL105.nvidia.com (10.27.9.14) with Microsoft SMTP Server (TLS) id 15.0.1497.38; Thu, 8 Sep 2022 01:55:37 +0000 Received: from [10.110.48.28] (10.126.231.35) by rnnvmail201.nvidia.com (10.129.68.8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.29; Wed, 7 Sep 2022 18:55:36 -0700 Message-ID: Date: Wed, 7 Sep 2022 18:58:52 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [PATCH] mm: avoid unnecessary page table walk for __get_user_pages Content-Language: en-US To: Andrew Morton , Chen Wandun CC: , , References: <20220906024401.133336-1-chenwandun@huawei.com> <20220907163408.f9a9152314d33afc74cb1f0c@linux-foundation.org> From: John Hubbard In-Reply-To: <20220907163408.f9a9152314d33afc74cb1f0c@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.126.231.35] X-ClientProxiedBy: rnnvmail203.nvidia.com (10.129.68.9) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1NAM11FT012:EE_|CY5PR12MB6300:EE_ X-MS-Office365-Filtering-Correlation-Id: 26a30307-5ef6-435f-7541-08da913d3a3f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: H959C0hlGbEjKzt3LpNngy8oVyvEQ4wQIDN6kxGOe4aCvDfRc2tkwIiAJ/PiWhmT927r9EMexOJ/DTsOalhjmnfnzzVeEqKvMhpyxv6UfUFFGcYO+/uXKaMgrAR9SOFlE0KKfrD6U6ie/XZ5BV4HWIiqhg6fNrVraaTJpIOvAR7loccDAzkFuwabz60WjhuXeQjBUmQYQJGwB0goWMVrN8j7rE/NfiQcr01zQqS6HU7lKZm9ZXqlNQEX+/dU2XiH2rNs1x/TY+IHcLUMM9JobdiaqKN3FjIzeTZm8idfBTTiVEYaKWlCXUpYGsKOUO9o7gS6ndPmMoy8DZRtmx0Anc7+P2PCmNXK5nXADGgumfwSgFUtzXuXXlQufDFhLSXkTESm3KM7gePN52JA/YCeHjYknDwDstnwsoPsV1nty2AAa+AO/yOTI/MtrkFk9k95VLqx1jLlLQxKoPEyDZkC818PJWeXiUuWg/pY9ygnDE6Qcxj/6ikuh52KRSXF9+e+sOX8Z4A9VDM0G1dxqhGGH0urntZ6d2rqoh5erCTDdRhNbubEeabat2Imhij9woUtM2HeMaog4bpIhhzbBSN+M/NqEUZR14mF9CIFF6x14nxlS8JfRbJp/0eYa4ZR0uW4tpUIyPnb5VO8oI1cHfytBTYwtIL79loQ14jan8eG5EuBM+opdSsWdHZzfq3Q2UwbmgnHDIs5gMuYw6YNj9oF6kx5tNQNGGgIOC0+Yql23WSIsaHs1pT6uu8U2pQy3FrlVwl3fPE6N2VE677C+7V383osP8ojEpjBkS4x/PW1BuFnYy2lw0Dthuq1bM1ijn+udkVwEBM1EJ0w+b3V07HcPA== X-Forefront-Antispam-Report: CIP:12.22.5.238;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:InfoNoRecords;CAT:NONE;SFS:(13230016)(4636009)(39860400002)(136003)(376002)(396003)(346002)(40470700004)(46966006)(36840700001)(31696002)(110136005)(26005)(86362001)(426003)(83380400001)(16526019)(356005)(186003)(336012)(47076005)(36860700001)(82740400003)(81166007)(2616005)(40460700003)(54906003)(82310400005)(2906002)(8936002)(40480700001)(31686004)(70206006)(4326008)(8676002)(36756003)(5660300002)(41300700001)(6666004)(16576012)(53546011)(316002)(70586007)(478600001)(36900700001)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Sep 2022 01:55:38.1678 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 26a30307-5ef6-435f-7541-08da913d3a3f X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[12.22.5.238];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT012.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6300 ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1662602141; a=rsa-sha256; cv=pass; b=VapnQp5oVOgpTqxMXc8Es+TaGhJgmkYWt7lUwWh4ohLB5QHcY9w6UM9wLifyfEXrThvmxc MPZWr3McMBF14Q5NJlAwtKk0Vq3zzNRLzTEqLOvktXuizrkWDGd+/86dGtAOo0+yojrbzY b3yctuxrmNmu13zjAa+al+7KzWhPR1M= ARC-Authentication-Results: i=2; imf17.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=P8GkI94X; spf=pass (imf17.hostedemail.com: domain of jhubbard@nvidia.com designates 40.107.102.46 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662602141; 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=hq/bpeg8tDWKR+NcspZOy+u7n2WvOpQMEGj1oAkqrO4=; b=kKIGYurLmExGSPvxwVTdWiabMzCoTG05NsRFFvxdaW4vaMoahJ4/VR+PICTMQSgyqUptyw KxEzNyxEalitaXuxjzIjlqkDc2exZIW+ksBQCi89DmFc5wKsZcf4wiHsArK/K4HKVtI8pM ZIUTZ1+Qu7a+T52ZZa/Z8CbkTlKxLrY= X-Stat-Signature: pa68zpjio4rrr3w6nrf9muejxrxkzfk7 X-Rspam-User: X-Rspamd-Queue-Id: 0B83240076 X-Rspamd-Server: rspam07 Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=P8GkI94X; spf=pass (imf17.hostedemail.com: domain of jhubbard@nvidia.com designates 40.107.102.46 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-HE-Tag: 1662602140-903266 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: On 9/7/22 16:34, Andrew Morton wrote: > On Tue, 6 Sep 2022 10:44:01 +0800 Chen Wandun wrote: > >> It is no need to walk page table and find pages if faultin_page success >> and __get_user_pages does't care pages at all, so directly handle next >> page. >> >> ... >> >> --- a/mm/gup.c >> +++ b/mm/gup.c >> @@ -1198,7 +1198,10 @@ static long __get_user_pages(struct mm_struct *mm, >> PTR_ERR(page) == -EMLINK, locked); >> switch (ret) { >> case 0: >> - goto retry; >> + if (pages) >> + goto retry; >> + else >> + goto next_page; Wow, good point. And it's been doing that for a *long* time! >> case -EBUSY: >> case -EAGAIN: >> ret = 0; > > Looks right to me. I redid the changelog somewhat: > > : There is no need to walk page tables and find pages if faultin_page)_ > : succeeds and __get_user_pages)_ doesn't care about populating the pages[] > : array. So directly go on to handle the next page. > > With that re-worded commit description, please feel to add Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA