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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: tietoevry.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: AS8PR04MB8199.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4ccd18e5-5244-4c01-36a9-08dce37e3f18 X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Oct 2024 07:37:34.3670 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: cbede638-a3d9-459f-8f4e-24ced73b4e5e X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: YM1vzZF74Tj85XXa6WwfdErlDkI3G23hJBuqCq8Q6oQQbZqfdtyDtnggwcaR+nl8GlT0/W6r5Gqtg7v5Yu8teDreXYwcIW0EPjyti7ZOx5M= X-MS-Exchange-Transport-CrossTenantHeadersStamped: VE1PR04MB7213 X-BeenThere: users@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK usage discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: users-bounces@dpdk.org Hi! Thanks.=20 According to chatgpt the descriptors are shared over all TX queues.=20 So, in a 4 TX queue and 1024 descriptors scenario I would be able to get ma= ximum 256 descriptors per TX queue (If I want same amount on all queues). B= ut if I only used 1 TX queue, I would get all 1024 descriptors on that sing= le TX queue. / Mikael -----Original Message----- From: Pathak, Pravin =20 Sent: Wednesday, October 2, 2024 6:07 PM To: Mikael R Carlsson ; Stephen Hemminger = Cc: users@dpdk.org Subject: RE: Relation between DPDK queue and descriptors [Du f?r inte e-post ofta fr?n pravin.pathak@intel.com. L?s om varf?r det h?= r ?r viktigt p? https://aka.ms/LearnAboutSenderIdentification ] Hi Mikael - ChatGpt provides a good description of the relation between these two. If y= ou ask ChatGPT to do a deep dive, it will provide a good bit of programming= and optimization details. Regards Pravin > -----Original Message----- > From: Mikael R Carlsson > Sent: Wednesday, October 2, 2024 12:05 PM > To: Stephen Hemminger > Cc: users@dpdk.org > Subject: RE: Relation between DPDK queue and descriptors > > Hi! > > Thanks for the response. > > I think I get the descriptor part, but what is the relation to queues?=20 > If the hardware supports 1024 descriptors and I need 6 queues, do I=20 > have 1024 descriptors on each TX queue? > > / Mikael > > > -----Original Message----- > From: Stephen Hemminger > Sent: Wednesday, October 2, 2024 5:29 PM > To: Mikael R Carlsson > Cc: users@dpdk.org > Subject: Re: Relation between DPDK queue and descriptors > > On Wed, 2 Oct 2024 15:21:45 +0000 > Mikael R Carlsson wrote: > > > Hi experts! > > > > I have a hard time to finds a good documentation about the relation > between DPDK TX queue and descriptors. > > > > Queue as in rte_eth_tx_queue_setup > > Descriptor as in rte_eth_dev_adjust_nb_rx_rx_desc > > > > We suspect we run out of descriptors in TX path, we are not sure=20 > > here. We > use more than one TX queue. Will we get more descriptors if we only=20 > use one single TX queue? Does anyone know if there is some good=20 > documentation regarding the TX queue and the descriptors? > > > > / Mikael > > > > A typical driver has a hardware ring buffer between the driver and the=20 > hardware. > One ring for transmit, and another for receive. > The entries in the ring are hardware specific data structure called descr= iptors. > Each descriptor usually has physical memory address, size, and flags. > > The number of Rx descriptors determines the number of unread frames=20 > the driver can hold. Too small, and you risk dropping packets; too=20 > large and under stress load the driver can end up buffering=20 > excessively causing latency (bufferbloat). > Similar on Tx but less of a problem because typically the network is=20 > faster than the application can send packets.