1.. SPDX-License-Identifier: BSD-3-Clause 2 Copyright(c) 2010-2014 Intel Corporation. 3 4.. _l2_fwd_event_app: 5 6L2 Forwarding Eventdev Sample Application 7========================================= 8 9The L2 Forwarding eventdev sample application is a simple example of packet 10processing using the Data Plane Development Kit (DPDK) to demonstrate usage of 11poll and event mode packet I/O mechanism. 12 13Overview 14-------- 15 16The L2 Forwarding eventdev sample application, performs L2 forwarding for each 17packet that is received on an RX_PORT. The destination port is the adjacent port 18from the enabled portmask, that is, if the first four ports are enabled (portmask=0x0f), 19ports 1 and 2 forward into each other, and ports 3 and 4 forward into each other. 20Also, if MAC addresses updating is enabled, the MAC addresses are affected as follows: 21 22* The source MAC address is replaced by the TX_PORT MAC address 23 24* The destination MAC address is replaced by 02:00:00:00:00:TX_PORT_ID 25 26Application receives packets from RX_PORT using below mentioned methods: 27 28* Poll mode 29 30* Eventdev mode (default) 31 32This application can be used to benchmark performance using a traffic-generator, 33as shown in the :numref:`figure_l2fwd_event_benchmark_setup`. 34 35.. _figure_l2fwd_event_benchmark_setup: 36 37.. figure:: img/l2_fwd_benchmark_setup.* 38 39 Performance Benchmark Setup (Basic Environment) 40 41Compiling the Application 42------------------------- 43 44To compile the sample application see :doc:`compiling`. 45 46The application is located in the ``l2fwd-event`` sub-directory. 47 48Running the Application 49----------------------- 50 51The application requires a number of command line options: 52 53.. code-block:: console 54 55 ./<build_dir>/examples/dpdk-l2fwd-event [EAL options] -- -p PORTMASK 56 [-q NQ] 57 [--[no-]mac-updating] 58 [--mode=MODE] 59 [--eventq-sched=SCHED_MODE] 60 [--event-vector [--event-vector-size SIZE] [--event-vector-tmo NS]] 61 62where, 63 64* p PORTMASK: A hexadecimal bitmask of the ports to configure 65 66* q NQ: Maximum number of queues per lcore (default is 1) 67 68* --[no-]mac-updating: Enable or disable MAC addresses updating (enabled by default). 69 70* --mode=MODE: Packet transfer mode for I/O, poll or eventdev. Eventdev by default. 71 72* --eventq-sched=SCHED_MODE: Event queue schedule mode, Ordered, Atomic or Parallel. Atomic by default. 73 74* --config: Configure forwarding port pair mapping. Alternate port pairs by default. 75 76* --event-vector: Enable event vectorization. Only valid if --mode=eventdev. 77 78* --event-vector-size: Max vector size if event vectorization is enabled. 79 80* --event-vector-tmo: Max timeout to form vector in nanoseconds if event vectorization is enabled. 81 82Sample usage commands are given below to run the application into different mode: 83 84Poll mode with 4 lcores, 16 ports and 8 RX queues per lcore and MAC address updating enabled, 85issue the command: 86 87.. code-block:: console 88 89 ./<build_dir>/examples/dpdk-l2fwd-event -l 0-3 -n 4 -- -q 8 -p ffff --mode=poll 90 91Eventdev mode with 4 lcores, 16 ports , sched method ordered and MAC address updating enabled, 92issue the command: 93 94.. code-block:: console 95 96 ./<build_dir>/examples/dpdk-l2fwd-event -l 0-3 -n 4 -- -p ffff --eventq-sched=ordered 97 98or 99 100.. code-block:: console 101 102 ./<build_dir>/examples/dpdk-l2fwd-event -l 0-3 -n 4 -- -q 8 -p ffff --mode=eventdev --eventq-sched=ordered 103 104Refer to the *DPDK Getting Started Guide* for general information on running 105applications and the Environment Abstraction Layer (EAL) options. 106 107To run application with S/W scheduler, it uses following DPDK services: 108 109* Software scheduler 110* Rx adapter service function 111* Tx adapter service function 112 113Application needs service cores to run above mentioned services. Service cores 114must be provided as EAL parameters along with the --vdev=event_sw0 to enable S/W 115scheduler. Following is the sample command: 116 117.. code-block:: console 118 119 ./<build_dir>/examples/dpdk-l2fwd-event -l 0-7 -s 0-3 -n 4 --vdev event_sw0 -- -q 8 -p ffff --mode=eventdev --eventq-sched=ordered 120 121Explanation 122----------- 123 124The following sections provide some explanation of the code. 125 126.. _l2_fwd_event_app_cmd_arguments: 127 128Command Line Arguments 129~~~~~~~~~~~~~~~~~~~~~~ 130 131The L2 Forwarding eventdev sample application takes specific parameters, 132in addition to Environment Abstraction Layer (EAL) arguments. 133The preferred way to parse parameters is to use the getopt() function, 134since it is part of a well-defined and portable library. 135 136The parsing of arguments is done in the **l2fwd_parse_args()** function for non 137eventdev parameters and in **parse_eventdev_args()** for eventdev parameters. 138The method of argument parsing is not described here. Refer to the 139*glibc getopt(3)* man page for details. 140 141EAL arguments are parsed first, then application-specific arguments. 142This is done at the beginning of the main() function and eventdev parameters 143are parsed in eventdev_resource_setup() function during eventdev setup: 144 145.. literalinclude:: ../../../examples/l2fwd-event/main.c 146 :language: c 147 :start-after: Init EAL. 8< 148 :end-before: >8 End of init EAL. 149 :dedent: 1 150 151Mbuf Pool Initialization 152~~~~~~~~~~~~~~~~~~~~~~~~ 153 154Once the arguments are parsed, the mbuf pool is created. 155The mbuf pool contains a set of mbuf objects that will be used by the driver 156and the application to store network packet data: 157 158.. literalinclude:: ../../../examples/l2fwd-event/main.c 159 :language: c 160 :start-after: Create the mbuf pool. 8< 161 :end-before: >8 End of creation of mbuf pool. 162 :dedent: 1 163 164The rte_mempool is a generic structure used to handle pools of objects. 165In this case, it is necessary to create a pool that will be used by the driver. 166The number of allocated pkt mbufs is NB_MBUF, with a data room size of 167RTE_MBUF_DEFAULT_BUF_SIZE each. 168A per-lcore cache of 32 mbufs is kept. 169The memory is allocated in NUMA socket 0, 170but it is possible to extend this code to allocate one mbuf pool per socket. 171 172The rte_pktmbuf_pool_create() function uses the default mbuf pool and mbuf 173initializers, respectively rte_pktmbuf_pool_init() and rte_pktmbuf_init(). 174An advanced application may want to use the mempool API to create the 175mbuf pool with more control. 176 177.. _l2_fwd_event_app_drv_init: 178 179Driver Initialization 180~~~~~~~~~~~~~~~~~~~~~ 181 182The main part of the code in the main() function relates to the initialization 183of the driver. To fully understand this code, it is recommended to study the 184chapters that related to the Poll Mode and Event mode Driver in the 185*DPDK Programmer's Guide* - Rel 1.4 EAR and the *DPDK API Reference*. 186 187.. literalinclude:: ../../../examples/l2fwd-event/main.c 188 :language: c 189 :start-after: Reset l2fwd_dst_ports. 8< 190 :end-before: >8 End of reset l2fwd_dst_ports. 191 :dedent: 1 192 193The next step is to configure the RX and TX queues. For each port, there is only 194one RX queue (only one lcore is able to poll a given port). The number of TX 195queues depends on the number of available lcores. The rte_eth_dev_configure() 196function is used to configure the number of queues for a port: 197 198.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_common.c 199 :language: c 200 :start-after: Configure RX and TX queue. 8< 201 :end-before: >8 End of configuration RX and TX queue. 202 :dedent: 2 203 204RX Queue Initialization 205~~~~~~~~~~~~~~~~~~~~~~~ 206 207The application uses one lcore to poll one or several ports, depending on the -q 208option, which specifies the number of queues per lcore. 209 210For example, if the user specifies -q 4, the application is able to poll four 211ports with one lcore. If there are 16 ports on the target (and if the portmask 212argument is -p ffff ), the application will need four lcores to poll all the 213ports. 214 215.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_common.c 216 :language: c 217 :start-after: Using lcore to poll one or several ports. 8< 218 :end-before: >8 End of using lcore to poll one or several ports. 219 :dedent: 2 220 221The list of queues that must be polled for a given lcore is stored in a private 222structure called struct lcore_queue_conf. 223 224.. literalinclude:: ../../../examples/l2fwd/main.c 225 :language: c 226 :start-after: List of queues to be polled for a given lcore. 8< 227 :end-before: >8 End of list of queues to be polled for a given lcore. 228 229The values n_rx_port and rx_port_list[] are used in the main packet processing 230loop (see :ref:`l2_fwd_event_app_rx_tx_packets`). 231 232.. _l2_fwd_event_app_tx_init: 233 234TX Queue Initialization 235~~~~~~~~~~~~~~~~~~~~~~~ 236 237Each lcore should be able to transmit on any port. For every port, a single TX 238queue is initialized. 239 240.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_common.c 241 :language: c 242 :start-after: Init one TX queue on each port. 8< 243 :end-before: >8 End of init one TX queue on each port. 244 :dedent: 2 245 246To configure eventdev support, application setups following components: 247 248* Event dev 249* Event queue 250* Event Port 251* Rx/Tx adapters 252* Ethernet ports 253 254.. _l2_fwd_event_app_event_dev_init: 255 256Event device Initialization 257~~~~~~~~~~~~~~~~~~~~~~~~~~~ 258Application can use either H/W or S/W based event device scheduler 259implementation and supports single instance of event device. It configures event 260device as per below configuration 261 262.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_event_generic.c 263 :language: c 264 :start-after: Configures event device as per below configuration. 8< 265 :end-before: >8 End of configuration event device as per below configuration. 266 :dedent: 1 267 268In case of S/W scheduler, application runs eventdev scheduler service on service 269core. Application retrieves service id and finds the best possible service core to 270run S/W scheduler. 271 272.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_event.c 273 :language: c 274 :start-after: Running eventdev scheduler service on service core. 8< 275 :end-before: >8 End of running eventdev scheduler service on service core. 276 :dedent: 1 277 278Event queue Initialization 279~~~~~~~~~~~~~~~~~~~~~~~~~~ 280Each Ethernet device is assigned a dedicated event queue which will be linked 281to all available event ports i.e. each lcore can dequeue packets from any of the 282Ethernet ports. 283 284.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_event_generic.c 285 :language: c 286 :start-after: Event queue initialization. 8< 287 :end-before: >8 End of event queue initialization. 288 :dedent: 1 289 290In case of S/W scheduler, an extra event queue is created which will be used for 291Tx adapter service function for enqueue operation. 292 293.. _l2_fwd_app_event_port_init: 294 295Event port Initialization 296~~~~~~~~~~~~~~~~~~~~~~~~~ 297Each worker thread is assigned a dedicated event port for enq/deq operations 298to/from an event device. All event ports are linked with all available event 299queues. 300 301.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_event_generic.c 302 :language: c 303 :start-after: Event port initialization. 8< 304 :end-before: >8 End of event port initialization. 305 :dedent: 1 306 307In case of S/W scheduler, an extra event port is created by DPDK library which 308is retrieved by the application and same will be used by Tx adapter service. 309 310.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_event_generic.c 311 :language: c 312 :start-after: Extra port created. 8< 313 :end-before: >8 End of extra port created. 314 :dedent: 1 315 316Rx/Tx adapter Initialization 317~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 318Each Ethernet port is assigned a dedicated Rx/Tx adapter for H/W scheduler. Each 319Ethernet port's Rx queues are connected to its respective event queue at 320priority 0 via Rx adapter configuration and Ethernet port's tx queues are 321connected via Tx adapter. 322 323.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_event_internal_port.c 324 :language: c 325 :start-after: Assigned ethernet port. 8< 326 :end-before: >8 End of assigned ethernet port. 327 :dedent: 1 328 329For S/W scheduler instead of dedicated adapters, common Rx/Tx adapters are 330configured which will be shared among all the Ethernet ports. Also DPDK library 331need service cores to run internal services for Rx/Tx adapters. Application gets 332service id for Rx/Tx adapters and after successful setup it runs the services 333on dedicated service cores. 334 335.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_event.c 336 :language: c 337 :start-after: Gets service ID for RX/TX adapters. 8< 338 :end-before: >8 End of get service ID for RX/TX adapters. 339 :dedent: 1 340 341.. _l2_fwd_event_app_rx_tx_packets: 342 343Receive, Process and Transmit Packets 344~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 345 346In the **l2fwd_main_loop()** function, the main task is to read ingress packets from 347the RX queues. This is done using the following code: 348 349.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_poll.c 350 :language: c 351 :start-after: Reading ingress packets. 8< 352 :end-before: >8 End of reading ingress packets. 353 :dedent: 2 354 355Packets are read in a burst of size MAX_PKT_BURST. The rte_eth_rx_burst() 356function writes the mbuf pointers in a local table and returns the number of 357available mbufs in the table. 358 359Then, each mbuf in the table is processed by the l2fwd_simple_forward() 360function. The processing is very simple: process the TX port from the RX port, 361then replace the source and destination MAC addresses if MAC addresses updating 362is enabled. 363 364During the initialization process, a static array of destination ports 365(l2fwd_dst_ports[]) is filled such that for each source port, a destination port 366is assigned that is either the next or previous enabled port from the portmask. 367If number of ports are odd in portmask then packet from last port will be 368forwarded to first port i.e. if portmask=0x07, then forwarding will take place 369like p0--->p1, p1--->p2, p2--->p0. 370 371Also to optimize enqueue operation, l2fwd_simple_forward() stores incoming mbufs 372up to MAX_PKT_BURST. Once it reaches up to limit, all packets are transmitted to 373destination ports. 374 375.. literalinclude:: ../../../examples/l2fwd/main.c 376 :language: c 377 :start-after: Simple forward. 8< 378 :end-before: >8 End of simple forward. 379 380For this test application, the processing is exactly the same for all packets 381arriving on the same RX port. Therefore, it would have been possible to call 382the rte_eth_tx_buffer() function directly from the main loop to send all the 383received packets on the same TX port, using the burst-oriented send function, 384which is more efficient. 385 386However, in real-life applications (such as, L3 routing), 387packet N is not necessarily forwarded on the same port as packet N-1. 388The application is implemented to illustrate that, so the same approach can be 389reused in a more complex application. 390 391To ensure that no packets remain in the tables, each lcore does a draining of TX 392queue in its main loop. This technique introduces some latency when there are 393not many packets to send, however it improves performance: 394 395.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_poll.c 396 :language: c 397 :start-after: Draining TX queue in main loop. 8< 398 :end-before: >8 End of draining TX queue in main loop. 399 :dedent: 2 400 401In the **l2fwd_event_loop()** function, the main task is to read ingress 402packets from the event ports. This is done using the following code: 403 404.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_event.c 405 :language: c 406 :start-after: Read packet from eventdev. 8< 407 :end-before: >8 End of reading packets from eventdev. 408 :dedent: 2 409 410 411Before reading packets, deq_len is fetched to ensure correct allowed deq length 412by the eventdev. 413The rte_event_dequeue_burst() function writes the mbuf pointers in a local table 414and returns the number of available mbufs in the table. 415 416Then, each mbuf in the table is processed by the l2fwd_eventdev_forward() 417function. The processing is very simple: process the TX port from the RX port, 418then replace the source and destination MAC addresses if MAC addresses updating 419is enabled. 420 421During the initialization process, a static array of destination ports 422(l2fwd_dst_ports[]) is filled such that for each source port, a destination port 423is assigned that is either the next or previous enabled port from the portmask. 424If number of ports are odd in portmask then packet from last port will be 425forwarded to first port i.e. if portmask=0x07, then forwarding will take place 426like p0--->p1, p1--->p2, p2--->p0. 427 428l2fwd_eventdev_forward() does not stores incoming mbufs. Packet will forwarded 429be to destination ports via Tx adapter or generic event dev enqueue API 430depending H/W or S/W scheduler is used. 431 432.. literalinclude:: ../../../examples/l2fwd-event/l2fwd_event.c 433 :language: c 434 :start-after: Read packet from eventdev. 8< 435 :end-before: >8 End of reading packets from eventdev. 436 :dedent: 2 437