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Wed, 8 Jan 2025 21:05:16 +0000 Date: Wed, 8 Jan 2025 21:05:15 +0000 (GMT) From: Aaron Tomlin To: Jakub Kicinski cc: Aaron Tomlin , Florian Fainelli , ronak.doshi@broadcom.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, bcm-kernel-feedback-list@broadcom.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/1] vmxnet3: Adjust maximum Rx ring buffer size In-Reply-To: <20250107154647.4bcbae3c@kernel.org> Message-ID: <71e6ab28-be0d-b85c-900b-537295bc81d1@atomlin.com> References: <20250105213036.288356-1-atomlin@atomlin.com> <20250106154741.23902c1a@kernel.org> <031eafb1-4fa6-4008-92c3-0f6ecec7ce63@broadcom.com> <20250106165732.3310033e@kernel.org> <2f127a6d-7fa2-5e99-093f-40ab81ece5b1@atomlin.com> <20250107154647.4bcbae3c@kernel.org> Content-Type: text/plain; charset=US-ASCII X-ClientProxiedBy: LO4P265CA0320.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:390::13) To CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:70::10) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CWLP123MB3523:EE_|CWXP123MB2712:EE_ X-MS-Office365-Filtering-Correlation-Id: 99cff143-7b25-4d08-fe54-08dd302826ca X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|7416014|366016; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?lP+xqIERTLAUhpmresybcI57M/HVxK6O3EXsBX2Y96uWq9+czcdDzGgXs7rB?= =?us-ascii?Q?/+GJG8jxOwus6BhXifuzdQMlv8FKy0RpILogZToF4oZmKDZiyZXtvuzvqMKZ?= =?us-ascii?Q?gAU+PFAnORPlMwLa5fVxRTA11Xv60RPllohpYXx98qqYfooJXLelykXDK3S+?= =?us-ascii?Q?NIGFmr/MXx6SpbbrDm0zluf+HrwfgQM6eL0oRA8B+7PDvkIt3kl7F4ggX3/m?= =?us-ascii?Q?LOMfweMweW7wU74Y/FHtWmZLdUdODN9yUBd/2UBPOdrHb1YssI+zUGmZ/6/9?= =?us-ascii?Q?zy824FRJ14ZA4uJ3fLvzsds8u4UlWAYH+vQaHi+qApw0x3DYW9cSDXfwPAln?= =?us-ascii?Q?/Xy/FOi66nSNEtwEd2kSH3UHU0kGNaoivE36qfacusb8G3fjN/KJzMpeUxnb?= =?us-ascii?Q?C299ZzCZBHq+TY+dLBIU/CFDA67bUQw6dgPR/xkhzM8LV7kor6J4X/P+Re9O?= =?us-ascii?Q?qPbouP/6w7PwwzHLXSBO5+vWRrLtR0UvhGfxDxQO0JP85Po0/jRI8fqMuFbl?= =?us-ascii?Q?m3J2hi8plA9RbcMzB8kKQSkQ2r+imf+sUc7N17Jk7bPg+Q2lkD89EDwYHkhl?= =?us-ascii?Q?opdvA364Ys5p38BkrBBscZjFJs61vaoU4RDbuSn4wxPv00wmQRXPThpvE/rF?= =?us-ascii?Q?f27zbWPjGsFfw13aZkuFOIwt0bmuFch8gRLdtVMCc00ecfYD6AxXcp7i1MRl?= =?us-ascii?Q?b5pycCe84yGmZVPr2mWlaumh4cA0Dg4sf6vYWlTsr5uLy6mQGV6+etjivxDY?= =?us-ascii?Q?DP0IKy0/iaWOVU8RJts2S4+cXECI89lQq/K6ph2mDoqxEeX3j77zFAfmi38b?= =?us-ascii?Q?ubbWJbakOPejUwViyrvFhoTocOUXAgyblN5mQ9Jhu4kvDpY5Ah7dmI6Uwksy?= =?us-ascii?Q?9/XmTx28dky+hwtkH6+YtQiKiRv7rW0ZhNGxOdmMscIqMsSQt/5T5deYdlu4?= =?us-ascii?Q?kI6cqOVsgk8Y/loAVii7/D9wfoR3KUY5x7+fVLBcaUfYTzBHRCSVksLQkQ/N?= =?us-ascii?Q?P/6NAPc0E2r2Ayua9hYnuTE0qYzBeuD4DhVevIgEYOqGaUZLEu2KDw8wrQWi?= =?us-ascii?Q?UURcHJ9vxogTVPcdbCabF2MLFODptSAjrOYxEp+EQUnIaAm8NQ/cGZITfMmP?= =?us-ascii?Q?O1YdYyOKUyLte8ynZd8JFsqzdbJTBeSAArVqL+CL/yfkpidbpaJLWFVC+SV7?= =?us-ascii?Q?5udKnvLdLecXC3OnIw7i4pa+ztN+C5FuV0iYHKgLJAj4pss4V8eWwiOE7GXt?= =?us-ascii?Q?IedeP+r2M0c9D05mwvzVaweguV8tD54aShatZWbaFaae1QYMya97R10dmNIU?= =?us-ascii?Q?W5nS3rzIir4MIEs4bR3fre2YlfLkC02cOf6FLjkXx45sjNL8XclY2H0M8M3g?= =?us-ascii?Q?eKwAhTzEpgCKs9lpX/YKNbzpw3Ypq5S/KYPZ8A5jaPCI+meposvfZpOFV/GH?= =?us-ascii?Q?sVupDmqjQKCFAPVAEYC4B68S2FHAJw08f1dgA6Ywta7zM+LxVODi+iZ+zR6s?= =?us-ascii?Q?eEHnPupxzcbfsT/T73cqCncoeTC0cm9IW/wCad2YLxju5f/9FSi4NgatXQOe?= =?us-ascii?Q?FZB2taQchhFIbEnO/OQjNEO1H+XjHSiRsPrMJJFk?= X-OriginatorOrg: atomlin.com X-MS-Exchange-CrossTenant-Network-Message-Id: 99cff143-7b25-4d08-fe54-08dd302826ca X-MS-Exchange-CrossTenant-AuthSource: CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jan 2025 21:05:16.7663 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: e6a32402-7d7b-4830-9a2b-76945bbbcb57 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: HE5tp0texgO76StG8yuCozoRSIyOJZTRc7n/I2Xuax8PWrv4bbG26Jgq6MOORCSNPTV31SLjSfh63sXbYLT/Sw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CWXP123MB2712 On Tue, 7 Jan 2025, Jakub Kicinski wrote: > This is a bit of a weird driver. But we should distinguish the default > ring size, which yes, should not be too large, and max ring size which > can be large but user setting a large size risks the fact the > allocations will fail and device will not open. > > This driver seems to read the default size from the hypervisor, is that > the value that is too large in your case? Maybe we should min() it with > something reasonable? The max allowed to be set via ethtool can remain > high IMO > See vmxnet3_get_ringparam(). If I understand correctly, since commit 50a5ce3e7116a ("vmxnet3: add receive data ring support"), if the specified VMXNET3 adapter has support for the Rx Data ring feature then the maximum Rx Data buffer size is reported as VMXNET3_RXDATA_DESC_MAX_SIZE (i.e. 2048) by 'ethtool'. Furthermore, See vmxnet3_set_ringparam(). A user specified Rx mini value cannot be more than VMXNET3_RXDATA_DESC_MAX_SIZE. Indeed the Rx mini value in the context of VMXNET3 would be the size of the Rx Data ring buffer. See the following excerpt from vmxnet3_set_ringparam(). As far as I can tell, the Rx Data buffer cannot be more than VMXNET3_RXDATA_DESC_MAX_SIZE: 686 static int 687 vmxnet3_set_ringparam(struct net_device *netdev, 688 struct ethtool_ringparam *param, 689 struct kernel_ethtool_ringparam *kernel_param, 690 struct netlink_ext_ack *extack) 691 { : 760 new_rxdata_desc_size = 761 (param->rx_mini_pending + VMXNET3_RXDATA_DESC_SIZE_MASK) & 762 ~VMXNET3_RXDATA_DESC_SIZE_MASK; 763 new_rxdata_desc_size = min_t(u16, new_rxdata_desc_size, 764 VMXNET3_RXDATA_DESC_MAX_SIZE); Have I missed something? -- Aaron Tomlin