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Received: from SJ1PR12MB6075.namprd12.prod.outlook.com (2603:10b6:a03:45e::8) by IA0PR12MB8647.namprd12.prod.outlook.com (2603:10b6:208:480::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7113.18; Thu, 21 Dec 2023 21:34:21 +0000 Received: from SJ1PR12MB6075.namprd12.prod.outlook.com ([fe80::eb39:938e:7503:c21e]) by SJ1PR12MB6075.namprd12.prod.outlook.com ([fe80::eb39:938e:7503:c21e%3]) with mapi id 15.20.7113.019; Thu, 21 Dec 2023 21:34:20 +0000 From: Aurelien Aptel To: linux-nvme@lists.infradead.org, netdev@vger.kernel.org, sagi@grimberg.me, hch@lst.de, kbusch@kernel.org, axboe@fb.com, chaitanyak@nvidia.com, davem@davemloft.net, kuba@kernel.org Cc: aaptel@nvidia.com, aurelien.aptel@gmail.com, smalin@nvidia.com, malin1024@gmail.com, ogerlitz@nvidia.com, yorayz@nvidia.com, borisp@nvidia.com, galshalom@nvidia.com, mgurtovoy@nvidia.com, viro@zeniv.linux.org.uk Subject: [PATCH v22 03/20] iov_iter: skip copy if src == dst for direct data placement Date: Thu, 21 Dec 2023 21:33:41 +0000 Message-Id: <20231221213358.105704-4-aaptel@nvidia.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231221213358.105704-1-aaptel@nvidia.com> References: <20231221213358.105704-1-aaptel@nvidia.com> Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: LO4P123CA0547.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:319::16) To SJ1PR12MB6075.namprd12.prod.outlook.com (2603:10b6:a03:45e::8) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PR12MB6075:EE_|IA0PR12MB8647:EE_ X-MS-Office365-Filtering-Correlation-Id: d43cc5f4-c20e-43b1-09c0-08dc026c97d9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?xLphsLqcMzftzi5pL57d9ztOBgDDG77/KeXJW+9TPePZPKclomk7Vqf7tvUE?= =?us-ascii?Q?DftYu6pEqQHmgv1uu0Sq33W7OtkDRYcH3A876yPI/ZAFJ+HGrKiEj2XyaVd7?= =?us-ascii?Q?BNV0GVR5is4b5t0vTUPEoxrfP88H+yuF8YLzP6GO//ZqssdgcCx1OWrW664b?= =?us-ascii?Q?tAMRIASreApFN1R85UoiV6C4o6pbsh20h4revFiscPfGqIQFUb3kQcSgskVU?= =?us-ascii?Q?Uj8Fq0p50tD+xQhDaOed5GhY2qn7t/CA4XCjkknF0o6u7hkW2/GfX+XirxeY?= =?us-ascii?Q?8ywi3MjTCHdGMx9I2cILGRR037Pbu+MLhZwCbJ9HineEZdzICF7fF/rcESbn?= =?us-ascii?Q?LHngAkEXxxP8eqFf4jnDbn+pX3GNETY/wtbPo/MfXaQBYS6GBYeECisMm8Xv?= =?us-ascii?Q?KSvfDk97kqHZLo9Rg0iem06My6HqRFxKWxjgPcKRh+ryuUyZtG0k51YbVP0s?= =?us-ascii?Q?6yXcbMDg1bwMfDZG2f6h+zooVSLnNBc4kR+Tn/QBlDFdHIultPnmne7sXRtS?= =?us-ascii?Q?Pj74j2KYIEjruuGAJNwSwgcojAQwIWSnvWJr5bByZenCH2MfHzztu+7XOsJ0?= =?us-ascii?Q?xOS99ubZroYxMi1q58P28pqgrk6mClSLFu9raHZdkmRYEou+k9TvfHO38xdB?= =?us-ascii?Q?LBCAxCfqd7Zo3MFGktbmXbWGXPBX4nImZFzixpry+Na/wSqqb0XnHjR3Wnsm?= =?us-ascii?Q?3gMyp2uIhH7yl+fxj3ncYDonJOsreCwR8E0tsOa2tE6fSwIHf5l9g+u4iVQu?= =?us-ascii?Q?wkFdSmrkG/xcZn3Mnh7m1roLjWbMLrw9Axy5+m/x94tXcJQ1cGlgp7ufwdM3?= =?us-ascii?Q?8ODU0VzUDtlhqfSuG6/CGk+C1HNof8qa5YJX5LbKMG+VyBg6XRSzRRizxL11?= =?us-ascii?Q?L36Ce8B9ltd8RhgxM5nCoWL1+OUwlERR3i+9aguhHED3ZfZhEM1/hzRcwpqO?= =?us-ascii?Q?I0T2K9TiGvFk+UMWydoBoWOqUwSKbmwj7BBhE3aA+EjuIoJpeWN0GAJM/MTS?= =?us-ascii?Q?zq71cJ2SravaYQvueCV+PZibLNSC36597/cdWBZYHhZuSDE8Xwl6zImHBKS7?= =?us-ascii?Q?GYcwSHL+RpeZwWqsRtlcFX9BGAaVxXc4FEBtEkuQpob5yv6t5j8X6VoI8Ddg?= =?us-ascii?Q?Qt0RemYVlYymPD3RAoq+cdF0ph2ntRf9R7vz+yg5pCSHa00h1nQHaN3ESLjX?= =?us-ascii?Q?Cr1sNruYOmJY7zWMHg5gtEJCm29TKMSFJEo9SRN2kQgEjS/EPtkAoCuRyi/R?= =?us-ascii?Q?Tr0n++w+sJ8P/qROA6vzCwfsF1nL+AzkOOE/YfkdTU8g8FynBzhF34o7Qlm2?= =?us-ascii?Q?Tj7QdPnEtteyg6sfOyOZJAp5xDZIUALBjFDwFlJm0zvePcTHZ/7Os3SY7G82?= =?us-ascii?Q?stEbFrkttUrKQnUqJaf7koPybB7WGptAe194NldqiOerjYUXgBZXjJ9xXi5b?= =?us-ascii?Q?tbCZYg2uDgxzMZXuF8UwE0rDkdwne9lqr1c3UKKIvJjSUZ9lmyLwF/xWr7io?= =?us-ascii?Q?jh68yk8UYKVQfmF0KPpPnCmuTxSYlYNUG2pJy9+bbD6Zixd5Ic2VcYOez8w6?= =?us-ascii?Q?D7tnpOw47sf3ZOz1M+jgmSpMWO/erN5fXki5XZj9?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: d43cc5f4-c20e-43b1-09c0-08dc026c97d9 X-MS-Exchange-CrossTenant-AuthSource: SJ1PR12MB6075.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Dec 2023 21:34:20.8448 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: B7NRc0U0uriVOc00H0872gjEgVeyvV7f1xUNvgaMG3K2qPvFF4zO+p6IPHuE8r+RFQPTVFRsW9+DhItL/tnV0Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB8647 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231221_133426_681917_272F7D65 X-CRM114-Status: GOOD ( 10.39 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org From: Ben Ben-Ishay When using direct data placement (DDP) the NIC could write the payload directly into the destination buffer and constructs SKBs such that they point to this data. To skip copies when SKB data already resides in the destination buffer we check if (src == dst), and skip the copy when it's true. Signed-off-by: Ben Ben-Ishay Signed-off-by: Boris Pismenny Signed-off-by: Or Gerlitz Signed-off-by: Yoray Zack Signed-off-by: Shai Malin Signed-off-by: Aurelien Aptel Reviewed-by: Chaitanya Kulkarni --- lib/iov_iter.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 8ff6824a1005..b96d8b6f5818 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -62,7 +62,14 @@ static __always_inline size_t memcpy_to_iter(void *iter_to, size_t progress, size_t len, void *from, void *priv2) { - memcpy(iter_to, from + progress, len); + /* + * When using direct data placement (DDP) the hardware writes + * data directly to the destination buffer, and constructs + * IOVs such that they point to this data. + * Thus, when the src == dst we skip the memcpy. + */ + if (iter_to != from + progress) + memcpy(iter_to, from + progress, len); return 0; } -- 2.34.1