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