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31 L2 Forwarding Sample Application (in Real and Virtualized Environments) with core load statistics.
32 ==================================================================================================
34 The L2 Forwarding sample application is a simple example of packet processing using
35 the Data Plane Development Kit (DPDK) which
36 also takes advantage of Single Root I/O Virtualization (SR-IOV) features in a virtualized environment.
40 This application is a variation of L2 Forwarding sample application. It demonstrate possible
41 scheme of job stats library usage therefore some parts of this document is identical with original
42 L2 forwarding application.
47 The L2 Forwarding sample application, which can operate in real and virtualized environments,
48 performs L2 forwarding for each packet that is received.
49 The destination port is the adjacent port from the enabled portmask, that is,
50 if the first four ports are enabled (portmask 0xf),
51 ports 1 and 2 forward into each other, and ports 3 and 4 forward into each other.
52 Also, the MAC addresses are affected as follows:
54 * The source MAC address is replaced by the TX port MAC address
56 * The destination MAC address is replaced by 02:00:00:00:00:TX_PORT_ID
58 This application can be used to benchmark performance using a traffic-generator, as shown in the :numref:`figure_l2_fwd_benchmark_setup_jobstats`.
60 The application can also be used in a virtualized environment as shown in :numref:`figure_l2_fwd_virtenv_benchmark_setup_jobstats`.
62 The L2 Forwarding application can also be used as a starting point for developing a new application based on the DPDK.
64 .. _figure_l2_fwd_benchmark_setup_jobstats:
66 .. figure:: img/l2_fwd_benchmark_setup.*
68 Performance Benchmark Setup (Basic Environment)
70 .. _figure_l2_fwd_virtenv_benchmark_setup_jobstats:
72 .. figure:: img/l2_fwd_virtenv_benchmark_setup.*
74 Performance Benchmark Setup (Virtualized Environment)
77 Virtual Function Setup Instructions
78 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
80 This application can use the virtual function available in the system and
81 therefore can be used in a virtual machine without passing through
82 the whole Network Device into a guest machine in a virtualized scenario.
83 The virtual functions can be enabled in the host machine or the hypervisor with the respective physical function driver.
85 For example, in a Linux* host machine, it is possible to enable a virtual function using the following command:
87 .. code-block:: console
89 modprobe ixgbe max_vfs=2,2
91 This command enables two Virtual Functions on each of Physical Function of the NIC,
92 with two physical ports in the PCI configuration space.
93 It is important to note that enabled Virtual Function 0 and 2 would belong to Physical Function 0
94 and Virtual Function 1 and 3 would belong to Physical Function 1,
95 in this case enabling a total of four Virtual Functions.
97 Compiling the Application
98 -------------------------
100 #. Go to the example directory:
102 .. code-block:: console
104 export RTE_SDK=/path/to/rte_sdk
105 cd ${RTE_SDK}/examples/l2fwd-jobstats
107 #. Set the target (a default target is used if not specified). For example:
109 .. code-block:: console
111 export RTE_TARGET=x86_64-native-linuxapp-gcc
113 *See the DPDK Getting Started Guide* for possible RTE_TARGET values.
115 #. Build the application:
117 .. code-block:: console
121 Running the Application
122 -----------------------
124 The application requires a number of command line options:
126 .. code-block:: console
128 ./build/l2fwd-jobstats [EAL options] -- -p PORTMASK [-q NQ] [-l]
132 * p PORTMASK: A hexadecimal bitmask of the ports to configure
134 * q NQ: A number of queues (=ports) per lcore (default is 1)
136 * l: Use locale thousands separator when formatting big numbers.
138 To run the application in linuxapp environment with 4 lcores, 16 ports, 8 RX queues per lcore and
139 thousands separator printing, issue the command:
141 .. code-block:: console
143 $ ./build/l2fwd-jobstats -l 0-3 -n 4 -- -q 8 -p ffff -l
145 Refer to the *DPDK Getting Started Guide* for general information on running applications
146 and the Environment Abstraction Layer (EAL) options.
151 The following sections provide some explanation of the code.
153 Command Line Arguments
154 ~~~~~~~~~~~~~~~~~~~~~~
156 The L2 Forwarding sample application takes specific parameters,
157 in addition to Environment Abstraction Layer (EAL) arguments
158 (see `Running the Application`_).
159 The preferred way to parse parameters is to use the getopt() function,
160 since it is part of a well-defined and portable library.
162 The parsing of arguments is done in the l2fwd_parse_args() function.
163 The method of argument parsing is not described here.
164 Refer to the *glibc getopt(3)* man page for details.
166 EAL arguments are parsed first, then application-specific arguments.
167 This is done at the beginning of the main() function:
173 ret = rte_eal_init(argc, argv);
175 rte_exit(EXIT_FAILURE, "Invalid EAL arguments\n");
180 /* parse application arguments (after the EAL ones) */
182 ret = l2fwd_parse_args(argc, argv);
184 rte_exit(EXIT_FAILURE, "Invalid L2FWD arguments\n");
186 Mbuf Pool Initialization
187 ~~~~~~~~~~~~~~~~~~~~~~~~
189 Once the arguments are parsed, the mbuf pool is created.
190 The mbuf pool contains a set of mbuf objects that will be used by the driver
191 and the application to store network packet data:
195 /* create the mbuf pool */
196 l2fwd_pktmbuf_pool = rte_pktmbuf_pool_create("mbuf_pool", NB_MBUF,
197 MEMPOOL_CACHE_SIZE, 0, RTE_MBUF_DEFAULT_BUF_SIZE,
200 if (l2fwd_pktmbuf_pool == NULL)
201 rte_exit(EXIT_FAILURE, "Cannot init mbuf pool\n");
203 The rte_mempool is a generic structure used to handle pools of objects.
204 In this case, it is necessary to create a pool that will be used by the driver.
205 The number of allocated pkt mbufs is NB_MBUF, with a data room size of
206 RTE_MBUF_DEFAULT_BUF_SIZE each.
207 A per-lcore cache of MEMPOOL_CACHE_SIZE mbufs is kept.
208 The memory is allocated in rte_socket_id() socket,
209 but it is possible to extend this code to allocate one mbuf pool per socket.
211 The rte_pktmbuf_pool_create() function uses the default mbuf pool and mbuf
212 initializers, respectively rte_pktmbuf_pool_init() and rte_pktmbuf_init().
213 An advanced application may want to use the mempool API to create the
214 mbuf pool with more control.
216 Driver Initialization
217 ~~~~~~~~~~~~~~~~~~~~~
219 The main part of the code in the main() function relates to the initialization of the driver.
220 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver
221 in the *DPDK Programmer's Guide* and the *DPDK API Reference*.
225 nb_ports = rte_eth_dev_count();
228 rte_exit(EXIT_FAILURE, "No Ethernet ports - bye\n");
230 /* reset l2fwd_dst_ports */
232 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++)
233 l2fwd_dst_ports[portid] = 0;
238 * Each logical core is assigned a dedicated TX queue on each port.
240 for (portid = 0; portid < nb_ports; portid++) {
241 /* skip ports that are not enabled */
242 if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
245 if (nb_ports_in_mask % 2) {
246 l2fwd_dst_ports[portid] = last_port;
247 l2fwd_dst_ports[last_port] = portid;
254 rte_eth_dev_info_get((uint8_t) portid, &dev_info);
257 The next step is to configure the RX and TX queues.
258 For each port, there is only one RX queue (only one lcore is able to poll a given port).
259 The number of TX queues depends on the number of available lcores.
260 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
264 ret = rte_eth_dev_configure((uint8_t)portid, 1, 1, &port_conf);
266 rte_exit(EXIT_FAILURE, "Cannot configure device: "
270 The global configuration is stored in a static structure:
274 static const struct rte_eth_conf port_conf = {
277 .header_split = 0, /**< Header Split disabled */
278 .hw_ip_checksum = 0, /**< IP checksum offload disabled */
279 .hw_vlan_filter = 0, /**< VLAN filtering disabled */
280 .jumbo_frame = 0, /**< Jumbo Frame Support disabled */
281 .hw_strip_crc= 0, /**< CRC stripped by hardware */
285 .mq_mode = ETH_DCB_NONE
289 RX Queue Initialization
290 ~~~~~~~~~~~~~~~~~~~~~~~
292 The application uses one lcore to poll one or several ports, depending on the -q option,
293 which specifies the number of queues per lcore.
295 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
296 If there are 16 ports on the target (and if the portmask argument is -p ffff ),
297 the application will need four lcores to poll all the ports.
301 ret = rte_eth_rx_queue_setup(portid, 0, nb_rxd,
302 rte_eth_dev_socket_id(portid),
307 rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup:err=%d, port=%u\n",
308 ret, (unsigned) portid);
310 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
314 struct lcore_queue_conf {
316 unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE];
317 truct mbuf_table tx_mbufs[RTE_MAX_ETHPORTS];
319 struct rte_timer rx_timers[MAX_RX_QUEUE_PER_LCORE];
320 struct rte_jobstats port_fwd_jobs[MAX_RX_QUEUE_PER_LCORE];
322 struct rte_timer flush_timer;
323 struct rte_jobstats flush_job;
324 struct rte_jobstats idle_job;
325 struct rte_jobstats_context jobs_context;
327 rte_atomic16_t stats_read_pending;
329 } __rte_cache_aligned;
331 Values of struct lcore_queue_conf:
333 * n_rx_port and rx_port_list[] are used in the main packet processing loop
334 (see Section `Receive, Process and Transmit Packets`_ later in this chapter).
336 * rx_timers and flush_timer are used to ensure forced TX on low packet rate.
338 * flush_job, idle_job and jobs_context are librte_jobstats objects used for managing l2fwd jobs.
340 * stats_read_pending and lock are used during job stats read phase.
342 TX Queue Initialization
343 ~~~~~~~~~~~~~~~~~~~~~~~
345 Each lcore should be able to transmit on any port. For every port, a single TX queue is initialized.
349 /* init one TX queue on each port */
352 ret = rte_eth_tx_queue_setup(portid, 0, nb_txd,
353 rte_eth_dev_socket_id(portid),
356 rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup:err=%d, port=%u\n",
357 ret, (unsigned) portid);
359 Jobs statistics initialization
360 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
361 There are several statistics objects available:
363 * Flush job statistics
367 rte_jobstats_init(&qconf->flush_job, "flush", drain_tsc, drain_tsc,
370 rte_timer_init(&qconf->flush_timer);
371 ret = rte_timer_reset(&qconf->flush_timer, drain_tsc, PERIODICAL,
372 lcore_id, &l2fwd_flush_job, NULL);
375 rte_exit(1, "Failed to reset flush job timer for lcore %u: %s",
376 lcore_id, rte_strerror(-ret));
379 * Statistics per RX port
383 rte_jobstats_init(job, name, 0, drain_tsc, 0, MAX_PKT_BURST);
384 rte_jobstats_set_update_period_function(job, l2fwd_job_update_cb);
386 rte_timer_init(&qconf->rx_timers[i]);
387 ret = rte_timer_reset(&qconf->rx_timers[i], 0, PERIODICAL, lcore_id,
388 l2fwd_fwd_job, (void *)(uintptr_t)i);
391 rte_exit(1, "Failed to reset lcore %u port %u job timer: %s",
392 lcore_id, qconf->rx_port_list[i], rte_strerror(-ret));
395 Following parameters are passed to rte_jobstats_init():
397 * 0 as minimal poll period
399 * drain_tsc as maximum poll period
401 * MAX_PKT_BURST as desired target value (RX burst size)
406 The forwarding path is reworked comparing to original L2 Forwarding application.
407 In the l2fwd_main_loop() function three loops are placed.
412 rte_spinlock_lock(&qconf->lock);
415 rte_jobstats_context_start(&qconf->jobs_context);
418 * - Read stats_read_pending flag
419 * - check if some real job need to be executed
421 rte_jobstats_start(&qconf->jobs_context, &qconf->idle_job);
425 uint64_t now = rte_get_timer_cycles();
427 need_manage = qconf->flush_timer.expire < now;
428 /* Check if we was esked to give a stats. */
430 rte_atomic16_read(&qconf->stats_read_pending);
431 need_manage |= stats_read_pending;
433 for (i = 0; i < qconf->n_rx_port && !need_manage; i++)
434 need_manage = qconf->rx_timers[i].expire < now;
436 } while (!need_manage);
437 rte_jobstats_finish(&qconf->idle_job, qconf->idle_job.target);
440 rte_jobstats_context_finish(&qconf->jobs_context);
441 } while (likely(stats_read_pending == 0));
443 rte_spinlock_unlock(&qconf->lock);
447 First infinite for loop is to minimize impact of stats reading. Lock is only locked/unlocked when asked.
449 Second inner while loop do the whole jobs management. When any job is ready, the use rte_timer_manage() is used to call the job handler.
450 In this place functions l2fwd_fwd_job() and l2fwd_flush_job() are called when needed.
451 Then rte_jobstats_context_finish() is called to mark loop end - no other jobs are ready to execute. By this time stats are ready to be read
452 and if stats_read_pending is set, loop breaks allowing stats to be read.
454 Third do-while loop is the idle job (idle stats counter). Its only purpose is monitoring if any job is ready or stats job read is pending
455 for this lcore. Statistics from this part of code is considered as the headroom available for additional processing.
457 Receive, Process and Transmit Packets
458 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
460 The main task of l2fwd_fwd_job() function is to read ingress packets from the RX queue of particular port and forward it.
461 This is done using the following code:
465 total_nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst,
468 for (j = 0; j < total_nb_rx; j++) {
470 rte_prefetch0(rte_pktmbuf_mtod(m, void *));
471 l2fwd_simple_forward(m, portid);
474 Packets are read in a burst of size MAX_PKT_BURST.
475 Then, each mbuf in the table is processed by the l2fwd_simple_forward() function.
476 The processing is very simple: process the TX port from the RX port, then replace the source and destination MAC addresses.
478 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
480 After first read second try is issued.
484 if (total_nb_rx == MAX_PKT_BURST) {
485 const uint16_t nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst,
488 total_nb_rx += nb_rx;
489 for (j = 0; j < nb_rx; j++) {
491 rte_prefetch0(rte_pktmbuf_mtod(m, void *));
492 l2fwd_simple_forward(m, portid);
496 This second read is important to give job stats library a feedback how many packets was processed.
500 /* Adjust period time in which we are running here. */
501 if (rte_jobstats_finish(job, total_nb_rx) != 0) {
502 rte_timer_reset(&qconf->rx_timers[port_idx], job->period, PERIODICAL,
503 lcore_id, l2fwd_fwd_job, arg);
506 To maximize performance exactly MAX_PKT_BURST is expected (the target value) to be read for each l2fwd_fwd_job() call.
507 If total_nb_rx is smaller than target value job->period will be increased. If it is greater the period will be decreased.
511 In the following code, one line for getting the output port requires some explanation.
513 During the initialization process, a static array of destination ports (l2fwd_dst_ports[]) is filled such that for each source port,
514 a destination port is assigned that is either the next or previous enabled port from the portmask.
515 Naturally, the number of ports in the portmask must be even, otherwise, the application exits.
520 l2fwd_simple_forward(struct rte_mbuf *m, unsigned portid)
522 struct ether_hdr *eth;
526 dst_port = l2fwd_dst_ports[portid];
528 eth = rte_pktmbuf_mtod(m, struct ether_hdr *);
530 /* 02:00:00:00:00:xx */
532 tmp = ð->d_addr.addr_bytes[0];
534 *((uint64_t *)tmp) = 0x000000000002 + ((uint64_t) dst_port << 40);
538 ether_addr_copy(&l2fwd_ports_eth_addr[dst_port], ð->s_addr);
540 l2fwd_send_packet(m, (uint8_t) dst_port);
543 Then, the packet is sent using the l2fwd_send_packet (m, dst_port) function.
544 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
545 Therefore, it would have been possible to call the l2fwd_send_burst() function directly from the main loop
546 to send all the received packets on the same TX port,
547 using the burst-oriented send function, which is more efficient.
549 However, in real-life applications (such as, L3 routing),
550 packet N is not necessarily forwarded on the same port as packet N-1.
551 The application is implemented to illustrate that, so the same approach can be reused in a more complex application.
553 The l2fwd_send_packet() function stores the packet in a per-lcore and per-txport table.
554 If the table is full, the whole packets table is transmitted using the l2fwd_send_burst() function:
558 /* Send the packet on an output interface */
561 l2fwd_send_packet(struct rte_mbuf *m, uint8_t port)
563 unsigned lcore_id, len;
564 struct lcore_queue_conf *qconf;
566 lcore_id = rte_lcore_id();
567 qconf = &lcore_queue_conf[lcore_id];
568 len = qconf->tx_mbufs[port].len;
569 qconf->tx_mbufs[port].m_table[len] = m;
572 /* enough pkts to be sent */
574 if (unlikely(len == MAX_PKT_BURST)) {
575 l2fwd_send_burst(qconf, MAX_PKT_BURST, port);
579 qconf->tx_mbufs[port].len = len; return 0;
582 To ensure that no packets remain in the tables, the flush job exists. The l2fwd_flush_job()
583 is called periodically to for each lcore draining TX queue of each port.
584 This technique introduces some latency when there are not many packets to send,
585 however it improves performance:
590 l2fwd_flush_job(__rte_unused struct rte_timer *timer, __rte_unused void *arg)
594 struct lcore_queue_conf *qconf;
595 struct mbuf_table *m_table;
598 lcore_id = rte_lcore_id();
599 qconf = &lcore_queue_conf[lcore_id];
601 rte_jobstats_start(&qconf->jobs_context, &qconf->flush_job);
603 now = rte_get_timer_cycles();
604 lcore_id = rte_lcore_id();
605 qconf = &lcore_queue_conf[lcore_id];
606 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
607 m_table = &qconf->tx_mbufs[portid];
608 if (m_table->len == 0 || m_table->next_flush_time <= now)
611 l2fwd_send_burst(qconf, portid);
615 /* Pass target to indicate that this job is happy of time interval
616 * in which it was called. */
617 rte_jobstats_finish(&qconf->flush_job, qconf->flush_job.target);