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b=vzh437O3sUJltuUdotkmMdN50116ETUf3RpPIOwZZf7TVq2zE2NG8bnr0ge6HImnmbysg1vu+BKR9/VfcfVnnAnKt2jLKE7RWxfkAWRnEpvvSL3+1PLthmI/ds698pCaBL1zWOekczNqjg76f/bEqgNj0GsXG1nNmizMiiBlXIQ= Received: from PH7PR12MB8596.namprd12.prod.outlook.com (2603:10b6:510:1b7::6) by SN7PR12MB8601.namprd12.prod.outlook.com (2603:10b6:806:26e::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8114.30; Wed, 6 Nov 2024 00:46:32 +0000 Received: from PH7PR12MB8596.namprd12.prod.outlook.com ([fe80::a011:943d:7291:8069]) by PH7PR12MB8596.namprd12.prod.outlook.com ([fe80::a011:943d:7291:8069%6]) with mapi id 15.20.8114.028; Wed, 6 Nov 2024 00:46:32 +0000 From: "Varghese, Vipin" To: Stephen Hemminger , "dev@dpdk.org" Subject: RE: RFC - Tap io_uring PMD Thread-Topic: RFC - Tap io_uring PMD Thread-Index: AQHbKxajHzUeG1wcGUaKU9U1Rl+dobKpcvsw Date: Wed, 6 Nov 2024 00:46:32 +0000 Message-ID: References: <20241030145644.0b97f23c@hermes.local> In-Reply-To: <20241030145644.0b97f23c@hermes.local> Accept-Language: en-IN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f265efc6-e181-49d6-80f4-fae95cf838a0_ActionId=605e39d6-ac59-444e-8a94-fae317ca7847; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: PH7PR12MB8596.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: dd987ffe-9d02-4d57-0f4b-08dcfdfc7541 X-MS-Exchange-CrossTenant-originalarrivaltime: 06 Nov 2024 00:46:32.0458 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: mjPAL8kfXfbuxEztyf8pWY1BzL4zUHTqVkfEwNhxqpAqs2DAPVr8KH9lkL7Ug1PXOYXcHZZxLsOn1TJXSFdFSQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB8601 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 [Public] Snipped > > > The current tap device is slow both due to architectural choices and the = overhead of > Linux system calls. I am exploring a how to fix that but some of the choi= ces require > some tradeoffs. Which leads to some open questions: > > 1. DPDK tap also support tunnel (TUN) mode where there is no Ethernet hea= der > only L3. Does anyone actually use this? It is different than what ever= y other > PMD expects. Hi Stephen, TUN interface were added in 2017 to support couple of use cases= in teleco (ipsec tunneling) based on actual uses cases from user space sta= ck. But I am not sure if anyone is using the same now. Follow up question, is not TUN rx-tx sperate function from TAP? Note: I am open to get this removed or separated if it is not used much. > > 2. The fastest way to use kernel TAP device would be to use io_uring. > But this was added in 5.1 kernel (2019). Rather than having conditiona= l or > dual mode in DPDK tap device, perhaps there should just be a new PMD > tap_uring? > > 3. Current TAP device provides hooks for several rte_flow types by playin= g > games with kernel qdisc. Does anyone really use this? Propose just not= doing > this in new tap_uring. > > 4. What other features of TAP device beyond basic send/receive make sense= ? > It looks like new device could support better statistics. > > 5. What about Rx interrupt support? > > Probably the hardest part of using io_uring is figuring out how to collec= t completions. > The simplest way would be to handle all completions rx and tx in the rx_b= urst > function. For the above questions from 2 to 5, I do like the idea of exploring better= alternatives.