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Wed, 9 Feb 2022 04:35:54 +0000 Received: from AM8PR08MB5810.eurprd08.prod.outlook.com ([fe80::6c76:b772:2b9d:75bf]) by AM8PR08MB5810.eurprd08.prod.outlook.com ([fe80::6c76:b772:2b9d:75bf%7]) with mapi id 15.20.4951.019; Wed, 9 Feb 2022 04:35:53 +0000 From: Honnappa Nagarahalli To: Beilei Xing , "dev@dpdk.org" CC: Feifei Wang , Ruifeng Wang , Ferruh Yigit , "bruce.richardson@intel.com" , nd , nd Subject: Questions on i40e TX path Thread-Topic: Questions on i40e TX path Thread-Index: AdgdbGSND9JeH63pReG8SPoILQbVuQ== Date: Wed, 9 Feb 2022 04:35:53 +0000 Message-ID: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ts-tracking-id: D17B15D36D1D2940A12CF083DB88F3D7.0 x-checkrecipientchecked: true Authentication-Results-Original: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=arm.com; X-MS-Office365-Filtering-Correlation-Id: ee96720a-bed2-4293-bba8-08d9eb85afd5 x-ms-traffictypediagnostic: DB8PR08MB3930:EE_|AM5EUR03FT052:EE_|AM4PR08MB2660:EE_ X-Microsoft-Antispam-PRVS: x-checkrecipientrouted: true nodisclaimer: true x-ms-oob-tlc-oobclassifiers: OLM:9508;OLM:9508; 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CTRY:IE; LANG:en; SCL:1; SRV:; IPV:CAL; SFV:NSPM; H:64aa7808-outbound-1.mta.getcheckrecipient.com; PTR:ec2-63-35-35-123.eu-west-1.compute.amazonaws.com; CAT:NONE; SFS:(13230001)(4636009)(40470700004)(36840700001)(46966006)(356005)(508600001)(4744005)(70206006)(82310400004)(36860700001)(186003)(26005)(316002)(110136005)(8936002)(54906003)(70586007)(86362001)(8676002)(4326008)(55016003)(40460700003)(5660300002)(52536014)(81166007)(33656002)(7696005)(336012)(47076005)(6506007)(9686003)(2906002); DIR:OUT; SFP:1101; X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Feb 2022 04:36:06.2208 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ee96720a-bed2-4293-bba8-08d9eb85afd5 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d; Ip=[63.35.35.123]; Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: AM5EUR03FT052.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM4PR08MB2660 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Hi Beilei, I want to make sure my understanding of the TX path is correct. Following = is my understanding. 1) The RS bit must be set in the TX descriptors to ask the NIC to report ba= ck the send status. 2) The NIC reports the send completion by setting the DTYPE field to 0xf. T= his also indicates that all the earlier descriptors are also done sending t= he packets. 3) The check "if (txq->nb_tx_free < txq->tx_free_thresh)" is mainly to ensu= re that we do not check the "descriptor done" status too often. Is my understanding correct? Thank you, Honnappa