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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 -c f -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 */
197 rte_mempool_create("mbuf_pool", NB_MBUF,
199 sizeof(struct rte_pktmbuf_pool_private),
200 rte_pktmbuf_pool_init, NULL,
201 rte_pktmbuf_init, NULL,
204 if (l2fwd_pktmbuf_pool == NULL)
205 rte_exit(EXIT_FAILURE, "Cannot init mbuf pool\n");
207 The rte_mempool is a generic structure used to handle pools of objects.
208 In this case, it is necessary to create a pool that will be used by the driver,
209 which expects to have some reserved space in the mempool structure,
210 sizeof(struct rte_pktmbuf_pool_private) bytes.
211 The number of allocated pkt mbufs is NB_MBUF, with a size of MBUF_SIZE each.
212 A per-lcore cache of 32 mbufs is kept.
213 The memory is allocated in rte_socket_id() socket,
214 but it is possible to extend this code to allocate one mbuf pool per socket.
216 Two callback pointers are also given to the rte_mempool_create() function:
218 * The first callback pointer is to rte_pktmbuf_pool_init() and is used
219 to initialize the private data of the mempool, which is needed by the driver.
220 This function is provided by the mbuf API, but can be copied and extended by the developer.
222 * The second callback pointer given to rte_mempool_create() is the mbuf initializer.
223 The default is used, that is, rte_pktmbuf_init(), which is provided in the rte_mbuf library.
224 If a more complex application wants to extend the rte_pktmbuf structure for its own needs,
225 a new function derived from rte_pktmbuf_init( ) can be created.
227 Driver Initialization
228 ~~~~~~~~~~~~~~~~~~~~~
230 The main part of the code in the main() function relates to the initialization of the driver.
231 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver
232 in the *DPDK Programmer's Guide* and the *DPDK API Reference*.
236 nb_ports = rte_eth_dev_count();
239 rte_exit(EXIT_FAILURE, "No Ethernet ports - bye\n");
241 if (nb_ports > RTE_MAX_ETHPORTS)
242 nb_ports = RTE_MAX_ETHPORTS;
244 /* reset l2fwd_dst_ports */
246 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++)
247 l2fwd_dst_ports[portid] = 0;
252 * Each logical core is assigned a dedicated TX queue on each port.
254 for (portid = 0; portid < nb_ports; portid++) {
255 /* skip ports that are not enabled */
256 if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
259 if (nb_ports_in_mask % 2) {
260 l2fwd_dst_ports[portid] = last_port;
261 l2fwd_dst_ports[last_port] = portid;
268 rte_eth_dev_info_get((uint8_t) portid, &dev_info);
271 The next step is to configure the RX and TX queues.
272 For each port, there is only one RX queue (only one lcore is able to poll a given port).
273 The number of TX queues depends on the number of available lcores.
274 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
278 ret = rte_eth_dev_configure((uint8_t)portid, 1, 1, &port_conf);
280 rte_exit(EXIT_FAILURE, "Cannot configure device: "
284 The global configuration is stored in a static structure:
288 static const struct rte_eth_conf port_conf = {
291 .header_split = 0, /**< Header Split disabled */
292 .hw_ip_checksum = 0, /**< IP checksum offload disabled */
293 .hw_vlan_filter = 0, /**< VLAN filtering disabled */
294 .jumbo_frame = 0, /**< Jumbo Frame Support disabled */
295 .hw_strip_crc= 0, /**< CRC stripped by hardware */
299 .mq_mode = ETH_DCB_NONE
303 RX Queue Initialization
304 ~~~~~~~~~~~~~~~~~~~~~~~
306 The application uses one lcore to poll one or several ports, depending on the -q option,
307 which specifies the number of queues per lcore.
309 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
310 If there are 16 ports on the target (and if the portmask argument is -p ffff ),
311 the application will need four lcores to poll all the ports.
315 ret = rte_eth_rx_queue_setup(portid, 0, nb_rxd,
316 rte_eth_dev_socket_id(portid),
321 rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup:err=%d, port=%u\n",
322 ret, (unsigned) portid);
324 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
328 struct lcore_queue_conf {
330 unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE];
331 truct mbuf_table tx_mbufs[RTE_MAX_ETHPORTS];
333 struct rte_timer rx_timers[MAX_RX_QUEUE_PER_LCORE];
334 struct rte_jobstats port_fwd_jobs[MAX_RX_QUEUE_PER_LCORE];
336 struct rte_timer flush_timer;
337 struct rte_jobstats flush_job;
338 struct rte_jobstats idle_job;
339 struct rte_jobstats_context jobs_context;
341 rte_atomic16_t stats_read_pending;
343 } __rte_cache_aligned;
345 Values of struct lcore_queue_conf:
347 * n_rx_port and rx_port_list[] are used in the main packet processing loop
348 (see Section `Receive, Process and Transmit Packets`_ later in this chapter).
350 * rx_timers and flush_timer are used to ensure forced TX on low packet rate.
352 * flush_job, idle_job and jobs_context are librte_jobstats objects used for managing l2fwd jobs.
354 * stats_read_pending and lock are used during job stats read phase.
356 TX Queue Initialization
357 ~~~~~~~~~~~~~~~~~~~~~~~
359 Each lcore should be able to transmit on any port. For every port, a single TX queue is initialized.
363 /* init one TX queue on each port */
366 ret = rte_eth_tx_queue_setup(portid, 0, nb_txd,
367 rte_eth_dev_socket_id(portid),
370 rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup:err=%d, port=%u\n",
371 ret, (unsigned) portid);
373 Jobs statistics initialization
374 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
375 There are several statistics objects available:
377 * Flush job statistics
381 rte_jobstats_init(&qconf->flush_job, "flush", drain_tsc, drain_tsc,
384 rte_timer_init(&qconf->flush_timer);
385 ret = rte_timer_reset(&qconf->flush_timer, drain_tsc, PERIODICAL,
386 lcore_id, &l2fwd_flush_job, NULL);
389 rte_exit(1, "Failed to reset flush job timer for lcore %u: %s",
390 lcore_id, rte_strerror(-ret));
393 * Statistics per RX port
397 rte_jobstats_init(job, name, 0, drain_tsc, 0, MAX_PKT_BURST);
398 rte_jobstats_set_update_period_function(job, l2fwd_job_update_cb);
400 rte_timer_init(&qconf->rx_timers[i]);
401 ret = rte_timer_reset(&qconf->rx_timers[i], 0, PERIODICAL, lcore_id,
402 l2fwd_fwd_job, (void *)(uintptr_t)i);
405 rte_exit(1, "Failed to reset lcore %u port %u job timer: %s",
406 lcore_id, qconf->rx_port_list[i], rte_strerror(-ret));
409 Following parameters are passed to rte_jobstats_init():
411 * 0 as minimal poll period
413 * drain_tsc as maximum poll period
415 * MAX_PKT_BURST as desired target value (RX burst size)
420 The forwarding path is reworked comparing to original L2 Forwarding application.
421 In the l2fwd_main_loop() function three loops are placed.
426 rte_spinlock_lock(&qconf->lock);
429 rte_jobstats_context_start(&qconf->jobs_context);
432 * - Read stats_read_pending flag
433 * - check if some real job need to be executed
435 rte_jobstats_start(&qconf->jobs_context, &qconf->idle_job);
439 uint64_t now = rte_get_timer_cycles();
441 need_manage = qconf->flush_timer.expire < now;
442 /* Check if we was esked to give a stats. */
444 rte_atomic16_read(&qconf->stats_read_pending);
445 need_manage |= stats_read_pending;
447 for (i = 0; i < qconf->n_rx_port && !need_manage; i++)
448 need_manage = qconf->rx_timers[i].expire < now;
450 } while (!need_manage);
451 rte_jobstats_finish(&qconf->idle_job, qconf->idle_job.target);
454 rte_jobstats_context_finish(&qconf->jobs_context);
455 } while (likely(stats_read_pending == 0));
457 rte_spinlock_unlock(&qconf->lock);
461 First infinite for loop is to minimize impact of stats reading. Lock is only locked/unlocked when asked.
463 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.
464 In this place functions l2fwd_fwd_job() and l2fwd_flush_job() are called when needed.
465 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
466 and if stats_read_pending is set, loop breaks allowing stats to be read.
468 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
469 for this lcore. Statistics from this part of code is considered as the headroom available for additional processing.
471 Receive, Process and Transmit Packets
472 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
474 The main task of l2fwd_fwd_job() function is to read ingress packets from the RX queue of particular port and forward it.
475 This is done using the following code:
479 total_nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst,
482 for (j = 0; j < total_nb_rx; j++) {
484 rte_prefetch0(rte_pktmbuf_mtod(m, void *));
485 l2fwd_simple_forward(m, portid);
488 Packets are read in a burst of size MAX_PKT_BURST.
489 Then, each mbuf in the table is processed by the l2fwd_simple_forward() function.
490 The processing is very simple: process the TX port from the RX port, then replace the source and destination MAC addresses.
492 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
494 After first read second try is issued.
498 if (total_nb_rx == MAX_PKT_BURST) {
499 const uint16_t nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst,
502 total_nb_rx += nb_rx;
503 for (j = 0; j < nb_rx; j++) {
505 rte_prefetch0(rte_pktmbuf_mtod(m, void *));
506 l2fwd_simple_forward(m, portid);
510 This second read is important to give job stats library a feedback how many packets was processed.
514 /* Adjust period time in which we are running here. */
515 if (rte_jobstats_finish(job, total_nb_rx) != 0) {
516 rte_timer_reset(&qconf->rx_timers[port_idx], job->period, PERIODICAL,
517 lcore_id, l2fwd_fwd_job, arg);
520 To maximize performance exactly MAX_PKT_BURST is expected (the target value) to be read for each l2fwd_fwd_job() call.
521 If total_nb_rx is smaller than target value job->period will be increased. If it is greater the period will be decreased.
525 In the following code, one line for getting the output port requires some explanation.
527 During the initialization process, a static array of destination ports (l2fwd_dst_ports[]) is filled such that for each source port,
528 a destination port is assigned that is either the next or previous enabled port from the portmask.
529 Naturally, the number of ports in the portmask must be even, otherwise, the application exits.
534 l2fwd_simple_forward(struct rte_mbuf *m, unsigned portid)
536 struct ether_hdr *eth;
540 dst_port = l2fwd_dst_ports[portid];
542 eth = rte_pktmbuf_mtod(m, struct ether_hdr *);
544 /* 02:00:00:00:00:xx */
546 tmp = ð->d_addr.addr_bytes[0];
548 *((uint64_t *)tmp) = 0x000000000002 + ((uint64_t) dst_port << 40);
552 ether_addr_copy(&l2fwd_ports_eth_addr[dst_port], ð->s_addr);
554 l2fwd_send_packet(m, (uint8_t) dst_port);
557 Then, the packet is sent using the l2fwd_send_packet (m, dst_port) function.
558 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
559 Therefore, it would have been possible to call the l2fwd_send_burst() function directly from the main loop
560 to send all the received packets on the same TX port,
561 using the burst-oriented send function, which is more efficient.
563 However, in real-life applications (such as, L3 routing),
564 packet N is not necessarily forwarded on the same port as packet N-1.
565 The application is implemented to illustrate that, so the same approach can be reused in a more complex application.
567 The l2fwd_send_packet() function stores the packet in a per-lcore and per-txport table.
568 If the table is full, the whole packets table is transmitted using the l2fwd_send_burst() function:
572 /* Send the packet on an output interface */
575 l2fwd_send_packet(struct rte_mbuf *m, uint8_t port)
577 unsigned lcore_id, len;
578 struct lcore_queue_conf *qconf;
580 lcore_id = rte_lcore_id();
581 qconf = &lcore_queue_conf[lcore_id];
582 len = qconf->tx_mbufs[port].len;
583 qconf->tx_mbufs[port].m_table[len] = m;
586 /* enough pkts to be sent */
588 if (unlikely(len == MAX_PKT_BURST)) {
589 l2fwd_send_burst(qconf, MAX_PKT_BURST, port);
593 qconf->tx_mbufs[port].len = len; return 0;
596 To ensure that no packets remain in the tables, the flush job exists. The l2fwd_flush_job()
597 is called periodically to for each lcore draining TX queue of each port.
598 This technique introduces some latency when there are not many packets to send,
599 however it improves performance:
604 l2fwd_flush_job(__rte_unused struct rte_timer *timer, __rte_unused void *arg)
608 struct lcore_queue_conf *qconf;
609 struct mbuf_table *m_table;
612 lcore_id = rte_lcore_id();
613 qconf = &lcore_queue_conf[lcore_id];
615 rte_jobstats_start(&qconf->jobs_context, &qconf->flush_job);
617 now = rte_get_timer_cycles();
618 lcore_id = rte_lcore_id();
619 qconf = &lcore_queue_conf[lcore_id];
620 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
621 m_table = &qconf->tx_mbufs[portid];
622 if (m_table->len == 0 || m_table->next_flush_time <= now)
625 l2fwd_send_burst(qconf, portid);
629 /* Pass target to indicate that this job is happy of time interval
630 * in which it was called. */
631 rte_jobstats_finish(&qconf->flush_job, qconf->flush_job.target);