.. code-block:: console
- ./build/link_status_interrupt [EAL options] -- -p PORTMASK [-q NQ][-T PERIOD]
+ ./<build_dir>/examples/dpdk-link_status_interrupt [EAL options] -- -p PORTMASK [-q NQ][-T PERIOD]
where,
.. code-block:: console
- $ ./build/link_status_interrupt -l 0-3 -n 4-- -q 8 -p ffff
+ $ ./<build_dir>/examples/dpdk-link_status_interrupt -l 0-3 -n 4-- -q 8 -p ffff
Refer to the *DPDK Getting Started Guide* for general information on running applications
and the Environment Abstraction Layer (EAL) options.
To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver in the
*DPDK Programmer's Guide and the DPDK API Reference*.
-.. code-block:: c
-
- /*
- * Each logical core is assigned a dedicated TX queue on each port.
- */
-
- RTE_ETH_FOREACH_DEV(portid) {
- /* skip ports that are not enabled */
-
- if ((lsi_enabled_port_mask & (1 << portid)) == 0)
- continue;
-
- /* save the destination port id */
-
- if (nb_ports_in_mask % 2) {
- lsi_dst_ports[portid] = portid_last;
- lsi_dst_ports[portid_last] = portid;
- }
- else
- portid_last = portid;
-
- nb_ports_in_mask++;
-
- rte_eth_dev_info_get((uint8_t) portid, &dev_info);
- }
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: Each logical core is assigned a dedicated TX queue on each port. 8<
+ :end-before: >8 End of assigning logical core.
+ :dedent: 1
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_exit(EXIT_FAILURE, "Cannot configure device: err=%d, port=%u\n", ret, portid);
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: Configure RX and TX queues. 8<
+ :end-before: >8 End of configure RX and TX queues.
+ :dedent: 2
The global configuration is stored in a static structure:
-.. code-block:: c
-
- static const struct rte_eth_conf port_conf = {
- .rxmode = {
- .split_hdr_size = 0,
- },
- .txmode = {},
- .intr_conf = {
- .lsc = 1, /**< link status interrupt feature enabled */
- },
- };
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: Global configuration stored in a static structure. 8<
+ :end-before: >8 End of global configuration stored in a static structure.
Configuring lsc to 0 (the default) disables the generation of any link status change interrupts in kernel space
and no user space interrupt event is received.
The application can register one or more callbacks to a specific port and interrupt event.
An example callback function that has been written as indicated below.
-.. code-block:: c
-
- static void
- lsi_event_callback(uint16_t port_id, enum rte_eth_event_type type, void *param)
- {
- struct rte_eth_link link;
- int ret;
- char link_status[RTE_ETH_LINK_MAX_STR_LEN];
-
- RTE_SET_USED(param);
-
- printf("\n\nIn registered callback...\n");
-
- printf("Event type: %s\n", type == RTE_ETH_EVENT_INTR_LSC ? "LSC interrupt" : "unknown event");
-
- ret = rte_eth_link_get_nowait(port_id, &link);
- if (ret < 0) {
- printf("Failed to get port %d link status: %s\n\n",
- port_id, rte_strerror(-ret));
- } else {
- rte_eth_link_to_str(link_status, sizeof(link_status), &link);
- printf("Port %d %s\n", port_id, link_status);
- }
- }
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: lsi_event_callback 8<
+ :end-before: >8 End of registering one or more callbacks.
This function is called when a link status interrupt is present for the right port.
The port_id indicates which port the interrupt applies to.
The application registers the lsi_event_callback and a NULL parameter to the link status interrupt event on each port:
-.. code-block:: c
-
- rte_eth_dev_callback_register((uint8_t)portid, RTE_ETH_EVENT_INTR_LSC, lsi_event_callback, NULL);
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: RTE callback register. 8<
+ :end-before: >8 End of registering lsi interrupt callback.
+ :dedent: 2
This registration can be done only after calling the rte_eth_dev_configure() function and before calling any other function.
If lsc is initialized with 0, the callback is never called since no interrupt event would ever be present.
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, lsi_pktmbuf_pool);
- if (ret < 0)
- rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup: err=%d, port=%u\n", ret, portid);
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: RX queue initialization. 8<
+ :end-before: >8 End of RX queue initialization.
+ :dedent: 2
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]; unsigned tx_queue_id;
- struct mbuf_table tx_mbufs[LSI_MAX_PORTS];
- } rte_cache_aligned;
-
- struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE];
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: List of queues must be polled for a give lcore. 8<
+ :end-before: >8 End of list of queues to be polled.
The n_rx_port and rx_port_list[] fields are used in the main packet processing loop
(see `Receive, Process and Transmit Packets`_).
The global configuration for the RX queues is stored in a static structure:
-.. code-block:: c
-
- static const struct rte_eth_rxconf rx_conf = {
- .rx_thresh = {
- .pthresh = RX_PTHRESH,
- .hthresh = RX_HTHRESH,
- .wthresh = RX_WTHRESH,
- },
- };
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: List of queues must be polled for a give lcore. 8<
+ :end-before: >8 End of list of queues to be polled.
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 logical core on each port */
-
- fflush(stdout);
-
- ret = rte_eth_tx_queue_setup(portid, 0, nb_txd, rte_eth_dev_socket_id(portid), &tx_conf);
- if (ret < 0)
- rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup: err=%d,port=%u\n", ret, (unsigned) portid);
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: init one TX queue logical core on each port. 8<
+ :end-before: >8 End of init one TX queue.
+ :dedent: 2
The global configuration for TX queues is stored in a static structure:
In the lsi_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);
- port_statistics[portid].rx += nb_rx;
-
- for (j = 0; j < nb_rx; j++) {
- m = pkts_burst[j];
- rte_prefetch0(rte_pktmbuf_mtod(m, void *));
- lsi_simple_forward(m, portid);
- }
- }
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: Read packet from RX queues. 8<
+ :end-before: >8 End of reading packet from RX queues.
+ :dedent: 2
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.
If portId is odd, the first line subtracts one and the second line does nothing.
Therefore, 0 goes to 1, and 1 to 0, 2 goes to 3 and 3 to 2, and so on.
-.. code-block:: c
-
- static void
- lsi_simple_forward(struct rte_mbuf *m, unsigned portid)
- {
- struct rte_ether_hdr *eth;
- void *tmp;
- unsigned dst_port = lsi_dst_ports[portid];
-
- eth = rte_pktmbuf_mtod(m, struct rte_ether_hdr *);
-
- /* 02:00:00:00:00:xx */
-
- tmp = ð->d_addr.addr_bytes[0];
-
- *((uint64_t *)tmp) = 0x000000000002 + (dst_port << 40);
-
- /* src addr */
- rte_ether_addr_copy(&lsi_ports_eth_addr[dst_port], ð->s_addr);
-
- lsi_send_packet(m, dst_port);
- }
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: Replacing the source and destination MAC addresses. 8<
+ :end-before: >8 End of replacing the source and destination MAC addresses.
Then, the packet is sent using the lsi_send_packet(m, dst_port) function.
For this test application, the processing is exactly the same for all packets arriving on the same RX port.
The lsi_send_packet() function stores the packet in a per-lcore and per-txport table.
If the table is full, the whole packets table is transmitted using the lsi_send_burst() function:
-.. code-block:: c
-
- /* Send the packet on an output interface */
-
- static int
- lsi_send_packet(struct rte_mbuf *m, uint16_t port)
- {
- unsigned lcore_id, len;
- struct lcore_queue_conf *qconf;
-
- lcore_id = rte_lcore_id();
- qconf = &lcore_queue_conf[lcore_id];
- len = qconf->tx_mbufs[port].len;
- qconf->tx_mbufs[port].m_table[len] = m;
- len++;
-
- /* enough pkts to be sent */
-
- if (unlikely(len == MAX_PKT_BURST)) {
- lsi_send_burst(qconf, MAX_PKT_BURST, port);
- len = 0;
- }
- qconf->tx_mbufs[port].len = len;
-
- return 0;
- }
+.. literalinclude:: ../../../examples/l2fwd-crypto/main.c
+ :language: c
+ :start-after: Enqueue packets for TX and prepare them to be sent. 8<
+ :end-before: >8 End of Enqueuing packets for TX.
To ensure that no packets remain in the tables, each lcore does a draining of the 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)) {
- /* this could be optimized (use queueid instead of * portid), but it is not called so often */
-
- for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
- if (qconf->tx_mbufs[portid].len == 0)
- continue;
-
- lsi_send_burst(&lcore_queue_conf[lcore_id],
- qconf->tx_mbufs[portid].len, (uint8_t) portid);
- qconf->tx_mbufs[portid].len = 0;
- }
-
- /* 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 >= (uint64_t) timer_period)) {
- /* do this only on main core */
- if (lcore_id == rte_get_main_lcore()) {
- print_stats();
-
- /* reset the timer */
- timer_tsc = 0;
- }
- }
- }
- prev_tsc = cur_tsc;
- }
+.. literalinclude:: ../../../examples/link_status_interrupt/main.c
+ :language: c
+ :start-after: Draining TX queue in its main loop. 8<
+ :end-before: >8 End of draining TX queue in its main loop.
+ :dedent: 2
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