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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.0 Subject: Re: [GIT PULL] iov_iter: Improve page extraction (pin or just list) Content-Language: en-US To: Jens Axboe , David Howells CC: Al Viro , Christoph Hellwig , Matthew Wilcox , Jan Kara , "David Hildenbrand" , Jason Gunthorpe , "Logan Gunthorpe" , Jeff Layton , , , , References: <3351099.1675077249@warthog.procyon.org.uk> From: John Hubbard In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.126.231.37] 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: CO1NAM11FT100:EE_|BY5PR12MB4870:EE_ X-MS-Office365-Filtering-Correlation-Id: f44794c7-033e-4685-b9d7-08db030dc462 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:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230025)(4636009)(136003)(39860400002)(346002)(396003)(376002)(451199018)(36840700001)(40470700004)(46966006)(82310400005)(31686004)(2906002)(5660300002)(86362001)(47076005)(336012)(426003)(7416002)(83380400001)(8936002)(40460700003)(41300700001)(31696002)(356005)(36756003)(478600001)(26005)(186003)(53546011)(82740400003)(2616005)(36860700001)(7636003)(110136005)(54906003)(4326008)(70206006)(8676002)(40480700001)(70586007)(16576012)(316002)(16526019)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jan 2023 22:03:06.5757 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f44794c7-033e-4685-b9d7-08db030dc462 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT100.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR12MB4870 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2B46740004 X-Rspam-User: X-Stat-Signature: 4mxz9p7nco4xw9x3qiwr8ewqfe947bkk X-HE-Tag: 1675116188-653768 X-HE-Meta: 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 QrYGsrlw RQ9Ukc3cotgkZqoj3p36GIbfdhpFw1dUAiJ+mTydq2QrZFtI2xQRxQwrVN7HwZGu31fUWLfwMkx2cLhVRRAlhAZgiLsXPwLyiAburR8xYklE8fXlfzdGhBQbI64TZfOtBgMOG0dzRCrG0JX3Ho6pWX1ZqPwGcwHBe9cfH/71DMAABgyxxSX1mgSVpx3U1Um8/2rfZ/BL3mg0nxP+I5Sn1GHGNctB2I2DsUB0/dq8hSh3JJKiqTSucyTXl5EE3RAKxzW0E+nV7N8ReByfcJiLDAA4Y/Ko9QKfIpBrtzHFK7g9hN6GyoDRKaJSLNxRohGbRlnGMycKJiYAavJ62T7dvMCUplb3AgVapYTZS7HaX7i35j9cZoV4TUcffOA== 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 1/30/23 13:57, Jens Axboe wrote: >> This does cause about a 2.7% regression for me, using O_DIRECT on a raw >> block device. Looking at a perf diff, here's the top: >> >> +2.71% [kernel.vmlinux] [k] mod_node_page_state >> +2.22% [kernel.vmlinux] [k] iov_iter_extract_pages >> >> and these two are gone: >> >> 2.14% [kernel.vmlinux] [k] __iov_iter_get_pages_alloc >> 1.53% [kernel.vmlinux] [k] iov_iter_get_pages >> >> rest is mostly in the noise, but mod_node_page_state() sticks out like >> a sore thumb. They seem to be caused by the node stat accounting done >> in gup.c for FOLL_PIN. > > Confirmed just disabling the node_stat bits in mm/gup.c and now the > performance is back to the same levels as before. > > An almost 3% regression is a bit hard to swallow... This is something that we say when adding pin_user_pages_fast(), yes. I doubt that I can quickly find the email thread, but we measured it and weren't immediately able to come up with a way to make it faster. At this point, it's a good time to consider if there is any way to speed it up. But I wanted to confirm that you're absolutely right: the measurement sounds about right, and that's also the hotspot that we say, too. thanks, -- John Hubbard NVIDIA