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client-ip=216.228.117.161; helo=mail.nvidia.com; pr=C From: Parav Pandit To: CC: , , , Parav Pandit Date: Mon, 3 Jul 2023 02:44:06 +0300 Message-ID: <20230702234410.47546-4-parav@nvidia.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20230702234410.47546-1-parav@nvidia.com> References: <20230702234410.47546-1-parav@nvidia.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.126.230.35] X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6NAM11FT101:EE_|MN2PR12MB4549:EE_ X-MS-Office365-Filtering-Correlation-Id: 1a01438f-0f69-4edf-0432-08db7b564526 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:(13230028)(4636009)(396003)(39860400002)(376002)(346002)(136003)(451199021)(36840700001)(46966006)(40470700004)(40460700003)(2906002)(41300700001)(5660300002)(8676002)(8936002)(82310400005)(36756003)(40480700001)(86362001)(16526019)(186003)(2616005)(478600001)(107886003)(26005)(1076003)(6666004)(82740400003)(70206006)(47076005)(316002)(6916009)(4326008)(70586007)(36860700001)(7636003)(54906003)(356005)(336012)(426003)(83380400001);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Jul 2023 23:44:25.9018 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 1a01438f-0f69-4edf-0432-08db7b564526 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: DM6NAM11FT101.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB4549 Subject: [virtio-comment] [PATCH REQUIREMENTS v2 3/7] net-features: Add low latency receive queue requirements Add requirements for the low latency receive queue. Signed-off-by: Parav Pandit --- changelog: v0->v1: - clarified the requirements further - added line for the gro case - added design goals as the motivation for the requirements --- net-workstream/features-1.4.md | 45 +++++++++++++++++++++++++++++++++- 1 file changed, 44 insertions(+), 1 deletion(-) diff --git a/net-workstream/features-1.4.md b/net-workstream/features-1.4.md index 0c3202c..3e8b5a4 100644 --- a/net-workstream/features-1.4.md +++ b/net-workstream/features-1.4.md @@ -7,7 +7,7 @@ together is desired while updating the virtio net interface. # 2. Summary 1. Device counters visible to the driver -2. Low latency tx virtqueue for PCI transport +2. Low latency tx and rx virtqueues for PCI transport # 3. Requirements ## 3.1 Device counters @@ -114,3 +114,46 @@ struct vnet_data_desc desc[2]; 7. Ability to place all transmit completion together with it per packet stream transmit timestamp using single PCIe transcation. + +### 3.2.2 Low latency rx virtqueue +0. Design goal: + a. Keep packet metadata and buffer data together which is consumed by driver + layer and make it available in a single cache line of cpu + b. Instead of having per packet descriptors which is complex to scale for + the device, supply the page directly to the device to consume it based + on packet size +1. The device should be able to write a packet receive completion that consists + of struct virtio_net_hdr (or similar) and a buffer id using a single DMA write + PCIe TLP. +2. The device should be able to perform DMA writes of multiple packets + completions in a single DMA transaction up to the PCIe maximum write limit + in a transaction. +3. The device should be able to zero pad packet write completion to align it to + 64B or CPU cache line size whenever possible. +4. An example of the above DMA completion structure: + +``` +/* Constant size receive packet completion */ +struct vnet_rx_completion { + u16 flags; + u16 id; /* buffer id */ + u8 gso_type; + u8 reserved[3]; + le16 gso_hdr_len; + le16 gso_size; + le16 csum_start; + le16 csum_offset; + u16 reserved2; + u64 timestamp; /* explained later */ + u8 padding[]; +}; +``` +5. The driver should be able to post constant-size buffer pages on a receive + queue which can be consumed by the device for an incoming packet of any size + from 64B to 9K bytes. +6. The device should be able to know the constant buffer size at receive + virtqueue level instead of per buffer level. +7. The device should be able to indicate when a full page buffer is consumed, + which can be recycled by the driver when the packets from the completed + page is fully consumed. +8. The device should be able to consume multiple pages for a receive GSO stream. -- 2.26.2 This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/