From 14d7ea259aebaacfa9326e54e881ab0e550f6a6e Mon Sep 17 00:00:00 2001 From: Sunil Kumar Kori Date: Wed, 30 Oct 2019 22:33:47 +0530 Subject: [PATCH] doc: add application usage guide for l2fwd-event Add documentation for l2fwd-event example. Update release notes. Signed-off-by: Sunil Kumar Kori Acked-by: Nipun Gupta Acked-by: Jerin Jacob --- MAINTAINERS | 1 + doc/guides/rel_notes/release_19_11.rst | 6 + doc/guides/sample_app_ug/index.rst | 1 + doc/guides/sample_app_ug/intro.rst | 5 + doc/guides/sample_app_ug/l2_forward_event.rst | 698 ++++++++++++++++++ 5 files changed, 711 insertions(+) create mode 100644 doc/guides/sample_app_ug/l2_forward_event.rst diff --git a/MAINTAINERS b/MAINTAINERS index e34f05c60e..e8d79ea57d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -1507,6 +1507,7 @@ M: Sunil Kumar Kori M: Pavan Nikhilesh T: git://dpdk.org/next/dpdk-next-eventdev F: examples/l2fwd-event/ +F: doc/guides/sample_app_ug/l2_forward_event.rst F: examples/l3fwd/ F: doc/guides/sample_app_ug/l3_forward.rst diff --git a/doc/guides/rel_notes/release_19_11.rst b/doc/guides/rel_notes/release_19_11.rst index 67ae6f2a77..03e58e0ac7 100644 --- a/doc/guides/rel_notes/release_19_11.rst +++ b/doc/guides/rel_notes/release_19_11.rst @@ -242,6 +242,12 @@ New Features * Added a console command to testpmd app, ``show port (port_id) ptypes`` which gives ability to print port supported ptypes in different protocol layers. +* **Added new example l2fwd-event application.** + + Added an example application `l2fwd-event` that adds event device support to + traditional l2fwd example. It demonstrates usage of poll and event mode IO + mechanism under a single application. + Removed Items ------------- diff --git a/doc/guides/sample_app_ug/index.rst b/doc/guides/sample_app_ug/index.rst index a3737c118a..16ddabe692 100644 --- a/doc/guides/sample_app_ug/index.rst +++ b/doc/guides/sample_app_ug/index.rst @@ -26,6 +26,7 @@ Sample Applications User Guides l2_forward_crypto l2_forward_job_stats l2_forward_real_virtual + l2_forward_event l2_forward_cat l3_forward l3_forward_power_man diff --git a/doc/guides/sample_app_ug/intro.rst b/doc/guides/sample_app_ug/intro.rst index 0b4ab1ba41..6cd0342a1e 100644 --- a/doc/guides/sample_app_ug/intro.rst +++ b/doc/guides/sample_app_ug/intro.rst @@ -45,6 +45,11 @@ examples are highlighted below. forwarding, or ``l2fwd`` application does forwarding based on Ethernet MAC addresses like a simple switch. +* :doc:`Network Layer 2 forwarding`: The Network Layer 2 + forwarding, or ``l2fwd-event`` application does forwarding based on Ethernet MAC + addresses like a simple switch. It demonstrates usage of poll and event mode + IO mechanism under a single application. + * :doc:`Network Layer 3 forwarding`: The Network Layer3 forwarding, or ``l3fwd`` application does forwarding based on Internet Protocol, IPv4 or IPv6 like a simple router. diff --git a/doc/guides/sample_app_ug/l2_forward_event.rst b/doc/guides/sample_app_ug/l2_forward_event.rst new file mode 100644 index 0000000000..52a570b97e --- /dev/null +++ b/doc/guides/sample_app_ug/l2_forward_event.rst @@ -0,0 +1,698 @@ +.. SPDX-License-Identifier: BSD-3-Clause + Copyright(c) 2010-2014 Intel Corporation. + +.. _l2_fwd_event_app: + +L2 Forwarding Eventdev Sample Application +========================================= + +The L2 Forwarding eventdev sample application is a simple example of packet +processing using the Data Plane Development Kit (DPDK) to demonstrate usage of +poll and event mode packet I/O mechanism. + +Overview +-------- + +The L2 Forwarding eventdev sample application, performs L2 forwarding for each +packet that is received on an RX_PORT. The destination port is the adjacent port +from the enabled portmask, that is, if the first four ports are enabled (portmask=0x0f), +ports 1 and 2 forward into each other, and ports 3 and 4 forward into each other. +Also, if MAC addresses updating is enabled, the MAC addresses are affected as follows: + +* The source MAC address is replaced by the TX_PORT MAC address + +* The destination MAC address is replaced by 02:00:00:00:00:TX_PORT_ID + +Application receives packets from RX_PORT using below mentioned methods: + +* Poll mode + +* Eventdev mode (default) + +This application can be used to benchmark performance using a traffic-generator, +as shown in the :numref:`figure_l2fwd_event_benchmark_setup`. + +.. _figure_l2fwd_event_benchmark_setup: + +.. figure:: img/l2_fwd_benchmark_setup.* + + Performance Benchmark Setup (Basic Environment) + +Compiling the Application +------------------------- + +To compile the sample application see :doc:`compiling`. + +The application is located in the ``l2fwd-event`` sub-directory. + +Running the Application +----------------------- + +The application requires a number of command line options: + +.. code-block:: console + + ./build/l2fwd-event [EAL options] -- -p PORTMASK [-q NQ] --[no-]mac-updating --mode=MODE --eventq-sched=SCHED_MODE + +where, + +* p PORTMASK: A hexadecimal bitmask of the ports to configure + +* q NQ: A number of queues (=ports) per lcore (default is 1) + +* --[no-]mac-updating: Enable or disable MAC addresses updating (enabled by default). + +* --mode=MODE: Packet transfer mode for I/O, poll or eventdev. Eventdev by default. + +* --eventq-sched=SCHED_MODE: Event queue schedule mode, Ordered, Atomic or Parallel. Atomic by default. + +Sample usage commands are given below to run the application into different mode: + +Poll mode with 4 lcores, 16 ports and 8 RX queues per lcore and MAC address updating enabled, +issue the command: + +.. code-block:: console + + ./build/l2fwd-event -l 0-3 -n 4 -- -q 8 -p ffff --mode=poll + +Eventdev mode with 4 lcores, 16 ports , sched method ordered and MAC address updating enabled, +issue the command: + +.. code-block:: console + + ./build/l2fwd-event -l 0-3 -n 4 -- -p ffff --eventq-sched=ordered + +or + +.. code-block:: console + + ./build/l2fwd-event -l 0-3 -n 4 -- -q 8 -p ffff --mode=eventdev --eventq-sched=ordered + +Refer to the *DPDK Getting Started Guide* for general information on running +applications and the Environment Abstraction Layer (EAL) options. + +To run application with S/W scheduler, it uses following DPDK services: + +* Software scheduler +* Rx adapter service function +* Tx adapter service function + +Application needs service cores to run above mentioned services. Service cores +must be provided as EAL parameters along with the --vdev=event_sw0 to enable S/W +scheduler. Following is the sample command: + +.. code-block:: console + + ./build/l2fwd-event -l 0-7 -s 0-3 -n 4 ---vdev event_sw0 --q 8 -p ffff --mode=eventdev --eventq-sched=ordered + +Explanation +----------- + +The following sections provide some explanation of the code. + +.. _l2_fwd_event_app_cmd_arguments: + +Command Line Arguments +~~~~~~~~~~~~~~~~~~~~~~ + +The L2 Forwarding eventdev sample application takes specific parameters, +in addition to Environment Abstraction Layer (EAL) arguments. +The preferred way to parse parameters is to use the getopt() function, +since it is part of a well-defined and portable library. + +The parsing of arguments is done in the **l2fwd_parse_args()** function for non +eventdev parameters and in **parse_eventdev_args()** for eventdev parameters. +The method of argument parsing is not described here. Refer to the +*glibc getopt(3)* man page for details. + +EAL arguments are parsed first, then application-specific arguments. +This is done at the beginning of the main() function and eventdev parameters +are parsed in eventdev_resource_setup() function during eventdev setup: + +.. code-block:: c + + /* init EAL */ + + ret = rte_eal_init(argc, argv); + if (ret < 0) + rte_panic("Invalid EAL arguments\n"); + + argc -= ret; + argv += ret; + + /* parse application arguments (after the EAL ones) */ + + ret = l2fwd_parse_args(argc, argv); + if (ret < 0) + rte_panic("Invalid L2FWD arguments\n"); + . + . + . + + /* Parse eventdev command line options */ + ret = parse_eventdev_args(argc, argv); + if (ret < 0) + return ret; + + + + +.. _l2_fwd_event_app_mbuf_init: + +Mbuf Pool Initialization +~~~~~~~~~~~~~~~~~~~~~~~~ + +Once the arguments are parsed, the mbuf pool is created. +The mbuf pool contains a set of mbuf objects that will be used by the driver +and the application to store network packet data: + +.. code-block:: c + + /* create the mbuf pool */ + + l2fwd_pktmbuf_pool = rte_pktmbuf_pool_create("mbuf_pool", NB_MBUF, + MEMPOOL_CACHE_SIZE, 0, + RTE_MBUF_DEFAULT_BUF_SIZE, + rte_socket_id()); + if (l2fwd_pktmbuf_pool == NULL) + rte_panic("Cannot init mbuf pool\n"); + +The rte_mempool is a generic structure used to handle pools of objects. +In this case, it is necessary to create a pool that will be used by the driver. +The number of allocated pkt mbufs is NB_MBUF, with a data room size of +RTE_MBUF_DEFAULT_BUF_SIZE each. +A per-lcore cache of 32 mbufs is kept. +The memory is allocated in NUMA socket 0, +but it is possible to extend this code to allocate one mbuf pool per socket. + +The rte_pktmbuf_pool_create() function uses the default mbuf pool and mbuf +initializers, respectively rte_pktmbuf_pool_init() and rte_pktmbuf_init(). +An advanced application may want to use the mempool API to create the +mbuf pool with more control. + +.. _l2_fwd_event_app_drv_init: + +Driver Initialization +~~~~~~~~~~~~~~~~~~~~~ + +The main part of the code in the main() function relates to the initialization +of the driver. To fully understand this code, it is recommended to study the +chapters that related to the Poll Mode and Event mode Driver in the +*DPDK Programmer's Guide* - Rel 1.4 EAR and the *DPDK API Reference*. + +.. code-block:: c + + if (rte_pci_probe() < 0) + rte_panic("Cannot probe PCI\n"); + + /* reset l2fwd_dst_ports */ + + for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) + l2fwd_dst_ports[portid] = 0; + + last_port = 0; + + /* + * Each logical core is assigned a dedicated TX queue on each port. + */ + + RTE_ETH_FOREACH_DEV(portid) { + /* skip ports that are not enabled */ + + if ((l2fwd_enabled_port_mask & (1 << portid)) == 0) + continue; + + if (nb_ports_in_mask % 2) { + l2fwd_dst_ports[portid] = last_port; + l2fwd_dst_ports[last_port] = portid; + } + else + last_port = portid; + + nb_ports_in_mask++; + + rte_eth_dev_info_get((uint8_t) portid, &dev_info); + } + +Observe that: + +* rte_pci_probe() parses the devices on the PCI bus and initializes recognized + devices. + +The next step is to configure the RX and TX queues. For each port, there is only +one RX queue (only one lcore is able to poll a given port). The number of TX +queues depends on the number of available lcores. The rte_eth_dev_configure() +function is used to configure the number of queues for a port: + +.. code-block:: c + + ret = rte_eth_dev_configure((uint8_t)portid, 1, 1, &port_conf); + if (ret < 0) + rte_panic("Cannot configure device: err=%d, port=%u\n", + ret, portid); + +.. _l2_fwd_event_app_rx_init: + +RX Queue Initialization +~~~~~~~~~~~~~~~~~~~~~~~ + +The application uses one lcore to poll one or several ports, depending on the -q +option, which specifies the number of queues per lcore. + +For example, if the user specifies -q 4, the application is able to poll four +ports with one lcore. If there are 16 ports on the target (and if the portmask +argument is -p ffff ), the application will need four lcores to poll all the +ports. + +.. code-block:: c + + ret = rte_eth_rx_queue_setup((uint8_t) portid, 0, nb_rxd, SOCKET0, + &rx_conf, l2fwd_pktmbuf_pool); + if (ret < 0) + + rte_panic("rte_eth_rx_queue_setup: err=%d, port=%u\n", + ret, portid); + +The list of queues that must be polled for a given lcore is stored in a private +structure called struct lcore_queue_conf. + +.. code-block:: c + + struct lcore_queue_conf { + unsigned n_rx_port; + unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE]; + struct mbuf_table tx_mbufs[L2FWD_MAX_PORTS]; + } rte_cache_aligned; + + struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE]; + +The values n_rx_port and rx_port_list[] are used in the main packet processing +loop (see :ref:`l2_fwd_event_app_rx_tx_packets`). + +.. _l2_fwd_event_app_tx_init: + +TX Queue Initialization +~~~~~~~~~~~~~~~~~~~~~~~ + +Each lcore should be able to transmit on any port. For every port, a single TX +queue is initialized. + +.. code-block:: c + + /* init one TX queue on each port */ + + fflush(stdout); + + ret = rte_eth_tx_queue_setup((uint8_t) portid, 0, nb_txd, + rte_eth_dev_socket_id(portid), &tx_conf); + if (ret < 0) + rte_panic("rte_eth_tx_queue_setup:err=%d, port=%u\n", + ret, (unsigned) portid); + +To configure eventdev support, application setups following components: + +* Event dev +* Event queue +* Event Port +* Rx/Tx adapters +* Ethernet ports + +.. _l2_fwd_event_app_event_dev_init: + +Event device Initialization +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Application can use either H/W or S/W based event device scheduler +implementation and supports single instance of event device. It configures event +device as per below configuration + +.. code-block:: c + + struct rte_event_dev_config event_d_conf = { + .nb_event_queues = ethdev_count, /* Dedicated to each Ethernet port */ + .nb_event_ports = num_workers, /* Dedicated to each lcore */ + .nb_events_limit = 4096, + .nb_event_queue_flows = 1024, + .nb_event_port_dequeue_depth = 128, + .nb_event_port_enqueue_depth = 128 + }; + + ret = rte_event_dev_configure(event_d_id, &event_d_conf); + if (ret < 0) + rte_panic("Error in configuring event device\n"); + +In case of S/W scheduler, application runs eventdev scheduler service on service +core. Application retrieves service id and finds the best possible service core to +run S/W scheduler. + +.. code-block:: c + + rte_event_dev_info_get(evt_rsrc->event_d_id, &evdev_info); + if (evdev_info.event_dev_cap & RTE_EVENT_DEV_CAP_DISTRIBUTED_SCHED) { + ret = rte_event_dev_service_id_get(evt_rsrc->event_d_id, + &service_id); + if (ret != -ESRCH && ret != 0) + rte_panic("Error in starting eventdev service\n"); + l2fwd_event_service_enable(service_id); + } + +.. _l2_fwd_app_event_queue_init: + +Event queue Initialization +~~~~~~~~~~~~~~~~~~~~~~~~~~ +Each Ethernet device is assigned a dedicated event queue which will be linked +to all available event ports i.e. each lcore can dequeue packets from any of the +Ethernet ports. + +.. code-block:: c + + struct rte_event_queue_conf event_q_conf = { + .nb_atomic_flows = 1024, + .nb_atomic_order_sequences = 1024, + .event_queue_cfg = 0, + .schedule_type = RTE_SCHED_TYPE_ATOMIC, + .priority = RTE_EVENT_DEV_PRIORITY_HIGHEST + }; + + /* User requested sched mode */ + event_q_conf.schedule_type = eventq_sched_mode; + for (event_q_id = 0; event_q_id < ethdev_count; event_q_id++) { + ret = rte_event_queue_setup(event_d_id, event_q_id, + &event_q_conf); + if (ret < 0) + rte_panic("Error in configuring event queue\n"); + } + +In case of S/W scheduler, an extra event queue is created which will be used for +Tx adapter service function for enqueue operation. + +.. _l2_fwd_app_event_port_init: + +Event port Initialization +~~~~~~~~~~~~~~~~~~~~~~~~~ +Each worker thread is assigned a dedicated event port for enq/deq operations +to/from an event device. All event ports are linked with all available event +queues. + +.. code-block:: c + + struct rte_event_port_conf event_p_conf = { + .dequeue_depth = 32, + .enqueue_depth = 32, + .new_event_threshold = 4096 + }; + + for (event_p_id = 0; event_p_id < num_workers; event_p_id++) { + ret = rte_event_port_setup(event_d_id, event_p_id, + &event_p_conf); + if (ret < 0) + rte_panic("Error in configuring event port %d\n", event_p_id); + + ret = rte_event_port_link(event_d_id, event_p_id, NULL, + NULL, 0); + if (ret < 0) + rte_panic("Error in linking event port %d to queue\n", + event_p_id); + } + +In case of S/W scheduler, an extra event port is created by DPDK library which +is retrieved by the application and same will be used by Tx adapter service. + +.. code-block:: c + + ret = rte_event_eth_tx_adapter_event_port_get(tx_adptr_id, &tx_port_id); + if (ret) + rte_panic("Failed to get Tx adapter port id: %d\n", ret); + + ret = rte_event_port_link(event_d_id, tx_port_id, + &evt_rsrc.evq.event_q_id[ + evt_rsrc.evq.nb_queues - 1], + NULL, 1); + if (ret != 1) + rte_panic("Unable to link Tx adapter port to Tx queue:err=%d\n", + ret); + +.. _l2_fwd_event_app_adapter_init: + +Rx/Tx adapter Initialization +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Each Ethernet port is assigned a dedicated Rx/Tx adapter for H/W scheduler. Each +Ethernet port's Rx queues are connected to its respective event queue at +priority 0 via Rx adapter configuration and Ethernet port's tx queues are +connected via Tx adapter. + +.. code-block:: c + + RTE_ETH_FOREACH_DEV(port_id) { + if ((rsrc->enabled_port_mask & (1 << port_id)) == 0) + continue; + ret = rte_event_eth_rx_adapter_create(adapter_id, event_d_id, + &evt_rsrc->def_p_conf); + if (ret) + rte_panic("Failed to create rx adapter[%d]\n", + adapter_id); + + /* Configure user requested sched type*/ + eth_q_conf.ev.sched_type = rsrc->sched_type; + eth_q_conf.ev.queue_id = evt_rsrc->evq.event_q_id[q_id]; + ret = rte_event_eth_rx_adapter_queue_add(adapter_id, port_id, + -1, ð_q_conf); + if (ret) + rte_panic("Failed to add queues to Rx adapter\n"); + + ret = rte_event_eth_rx_adapter_start(adapter_id); + if (ret) + rte_panic("Rx adapter[%d] start Failed\n", adapter_id); + + evt_rsrc->rx_adptr.rx_adptr[adapter_id] = adapter_id; + adapter_id++; + if (q_id < evt_rsrc->evq.nb_queues) + q_id++; + } + + adapter_id = 0; + RTE_ETH_FOREACH_DEV(port_id) { + if ((rsrc->enabled_port_mask & (1 << port_id)) == 0) + continue; + ret = rte_event_eth_tx_adapter_create(adapter_id, event_d_id, + &evt_rsrc->def_p_conf); + if (ret) + rte_panic("Failed to create tx adapter[%d]\n", + adapter_id); + + ret = rte_event_eth_tx_adapter_queue_add(adapter_id, port_id, + -1); + if (ret) + rte_panic("Failed to add queues to Tx adapter\n"); + + ret = rte_event_eth_tx_adapter_start(adapter_id); + if (ret) + rte_panic("Tx adapter[%d] start Failed\n", adapter_id); + + evt_rsrc->tx_adptr.tx_adptr[adapter_id] = adapter_id; + adapter_id++; + } + +For S/W scheduler instead of dedicated adapters, common Rx/Tx adapters are +configured which will be shared among all the Ethernet ports. Also DPDK library +need service cores to run internal services for Rx/Tx adapters. Application gets +service id for Rx/Tx adapters and after successful setup it runs the services +on dedicated service cores. + +.. code-block:: c + + for (i = 0; i < evt_rsrc->rx_adptr.nb_rx_adptr; i++) { + ret = rte_event_eth_rx_adapter_caps_get(evt_rsrc->event_d_id, + evt_rsrc->rx_adptr.rx_adptr[i], &caps); + if (ret < 0) + rte_panic("Failed to get Rx adapter[%d] caps\n", + evt_rsrc->rx_adptr.rx_adptr[i]); + ret = rte_event_eth_rx_adapter_service_id_get( + evt_rsrc->event_d_id, + &service_id); + if (ret != -ESRCH && ret != 0) + rte_panic("Error in starting Rx adapter[%d] service\n", + evt_rsrc->rx_adptr.rx_adptr[i]); + l2fwd_event_service_enable(service_id); + } + + for (i = 0; i < evt_rsrc->tx_adptr.nb_tx_adptr; i++) { + ret = rte_event_eth_tx_adapter_caps_get(evt_rsrc->event_d_id, + evt_rsrc->tx_adptr.tx_adptr[i], &caps); + if (ret < 0) + rte_panic("Failed to get Rx adapter[%d] caps\n", + evt_rsrc->tx_adptr.tx_adptr[i]); + ret = rte_event_eth_tx_adapter_service_id_get( + evt_rsrc->event_d_id, + &service_id); + if (ret != -ESRCH && ret != 0) + rte_panic("Error in starting Rx adapter[%d] service\n", + evt_rsrc->tx_adptr.tx_adptr[i]); + l2fwd_event_service_enable(service_id); + } + +.. _l2_fwd_event_app_rx_tx_packets: + +Receive, Process and Transmit Packets +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In the **l2fwd_main_loop()** function, the main task is to read ingress packets from +the RX queues. This is done using the following code: + +.. code-block:: c + + /* + * Read packet from RX queues + */ + + for (i = 0; i < qconf->n_rx_port; i++) { + portid = qconf->rx_port_list[i]; + nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst, + MAX_PKT_BURST); + + for (j = 0; j < nb_rx; j++) { + m = pkts_burst[j]; + rte_prefetch0(rte_pktmbuf_mtod(m, void *)); + l2fwd_simple_forward(m, portid); + } + } + +Packets are read in a burst of size MAX_PKT_BURST. The rte_eth_rx_burst() +function writes the mbuf pointers in a local table and returns the number of +available mbufs in the table. + +Then, each mbuf in the table is processed by the l2fwd_simple_forward() +function. The processing is very simple: process the TX port from the RX port, +then replace the source and destination MAC addresses if MAC addresses updating +is enabled. + +During the initialization process, a static array of destination ports +(l2fwd_dst_ports[]) is filled such that for each source port, a destination port +is assigned that is either the next or previous enabled port from the portmask. +If number of ports are odd in portmask then packet from last port will be +forwarded to first port i.e. if portmask=0x07, then forwarding will take place +like p0--->p1, p1--->p2, p2--->p0. + +Also to optimize enqueue operation, l2fwd_simple_forward() stores incoming mbufs +up to MAX_PKT_BURST. Once it reaches up to limit, all packets are transmitted to +destination ports. + +.. code-block:: c + + static void + l2fwd_simple_forward(struct rte_mbuf *m, uint32_t portid) + { + uint32_t dst_port; + int32_t sent; + struct rte_eth_dev_tx_buffer *buffer; + + dst_port = l2fwd_dst_ports[portid]; + + if (mac_updating) + l2fwd_mac_updating(m, dst_port); + + buffer = tx_buffer[dst_port]; + sent = rte_eth_tx_buffer(dst_port, 0, buffer, m); + if (sent) + port_statistics[dst_port].tx += sent; + } + +For this test application, the processing is exactly the same for all packets +arriving on the same RX port. Therefore, it would have been possible to call +the rte_eth_tx_buffer() function directly from the main loop to send all the +received packets on the same TX port, using the burst-oriented send function, +which is more efficient. + +However, in real-life applications (such as, L3 routing), +packet N is not necessarily forwarded on the same port as packet N-1. +The application is implemented to illustrate that, so the same approach can be +reused in a more complex application. + +To ensure that no packets remain in the tables, each lcore does a draining of TX +queue in its main loop. This technique introduces some latency when there are +not many packets to send, however it improves performance: + +.. code-block:: c + + cur_tsc = rte_rdtsc(); + + /* + * TX burst queue drain + */ + diff_tsc = cur_tsc - prev_tsc; + if (unlikely(diff_tsc > drain_tsc)) { + for (i = 0; i < qconf->n_rx_port; i++) { + portid = l2fwd_dst_ports[qconf->rx_port_list[i]]; + buffer = tx_buffer[portid]; + sent = rte_eth_tx_buffer_flush(portid, 0, + buffer); + if (sent) + port_statistics[portid].tx += sent; + } + + /* if timer is enabled */ + if (timer_period > 0) { + /* advance the timer */ + timer_tsc += diff_tsc; + + /* if timer has reached its timeout */ + if (unlikely(timer_tsc >= timer_period)) { + /* do this only on master core */ + if (lcore_id == rte_get_master_lcore()) { + print_stats(); + /* reset the timer */ + timer_tsc = 0; + } + } + } + + prev_tsc = cur_tsc; + } + +In the **l2fwd_event_loop()** function, the main task is to read ingress +packets from the event ports. This is done using the following code: + +.. code-block:: c + + /* Read packet from eventdev */ + nb_rx = rte_event_dequeue_burst(event_d_id, event_p_id, + events, deq_len, 0); + if (nb_rx == 0) { + rte_pause(); + continue; + } + + for (i = 0; i < nb_rx; i++) { + mbuf[i] = events[i].mbuf; + rte_prefetch0(rte_pktmbuf_mtod(mbuf[i], void *)); + } + + +Before reading packets, deq_len is fetched to ensure correct allowed deq length +by the eventdev. +The rte_event_dequeue_burst() function writes the mbuf pointers in a local table +and returns the number of available mbufs in the table. + +Then, each mbuf in the table is processed by the l2fwd_eventdev_forward() +function. The processing is very simple: process the TX port from the RX port, +then replace the source and destination MAC addresses if MAC addresses updating +is enabled. + +During the initialization process, a static array of destination ports +(l2fwd_dst_ports[]) is filled such that for each source port, a destination port +is assigned that is either the next or previous enabled port from the portmask. +If number of ports are odd in portmask then packet from last port will be +forwarded to first port i.e. if portmask=0x07, then forwarding will take place +like p0--->p1, p1--->p2, p2--->p0. + +l2fwd_eventdev_forward() does not stores incoming mbufs. Packet will forwarded +be to destination ports via Tx adapter or generic event dev enqueue API +depending H/W or S/W scheduler is used. + +.. code-block:: c + + nb_tx = rte_event_eth_tx_adapter_enqueue(event_d_id, port_id, ev, + nb_rx); + while (nb_tx < nb_rx && !rsrc->force_quit) + nb_tx += rte_event_eth_tx_adapter_enqueue( + event_d_id, port_id, + ev + nb_tx, nb_rx - nb_tx); -- 2.20.1