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31 Distributor Sample Application
32 ==============================
34 The distributor sample application is a simple example of packet distribution
35 to cores using the Data Plane Development Kit (DPDK).
40 The distributor application performs the distribution of packets that are received
41 on an RX_PORT to different cores. When processed by the cores, the destination
42 port of a packet is the port from the enabled port mask adjacent to the one on
43 which the packet was received, that is, if the first four ports are enabled
44 (port mask 0xf), ports 0 and 1 RX/TX into each other, and ports 2 and 3 RX/TX
47 This application can be used to benchmark performance using the traffic
48 generator as shown in the figure below.
52 .. figure:: img/dist_perf.*
54 Performance Benchmarking Setup (Basic Environment)
56 Compiling the Application
57 -------------------------
59 To compile the sample application see :doc:`compiling`.
61 The application is located in the ``distributor`` sub-directory.
63 Running the Application
64 -----------------------
66 #. The application has a number of command line options:
68 .. code-block:: console
70 ./build/distributor_app [EAL options] -- -p PORTMASK
74 * -p PORTMASK: Hexadecimal bitmask of ports to configure
76 #. To run the application in linuxapp environment with 10 lcores, 4 ports,
79 .. code-block:: console
81 $ ./build/distributor_app -l 1-9,22 -n 4 -- -p f
83 #. Refer to the DPDK Getting Started Guide for general information on running
84 applications and the Environment Abstraction Layer (EAL) options.
89 The distributor application consists of four types of threads: a receive
90 thread (``lcore_rx()``), a distributor thread (``lcore_dist()``), a set of
91 worker threads (``lcore_worker()``), and a transmit thread(``lcore_tx()``).
92 How these threads work together is shown in :numref:`figure_dist_app` below.
93 The ``main()`` function launches threads of these four types. Each thread
94 has a while loop which will be doing processing and which is terminated
95 only upon SIGINT or ctrl+C.
97 The receive thread receives the packets using ``rte_eth_rx_burst()`` and will
98 enqueue them to an rte_ring. The distributor thread will dequeue the packets
99 from the ring and assign them to workers (using ``rte_distributor_process()`` API).
100 This assignment is based on the tag (or flow ID) of the packet - indicated by
101 the hash field in the mbuf. For IP traffic, this field is automatically filled
102 by the NIC with the "usr" hash value for the packet, which works as a per-flow
103 tag. The distributor thread communicates with the worker threads using a
104 cache-line swapping mechanism, passing up to 8 mbuf pointers at a time
105 (one cache line) to each worker.
107 More than one worker thread can exist as part of the application, and these
108 worker threads do simple packet processing by requesting packets from
109 the distributor, doing a simple XOR operation on the input port mbuf field
110 (to indicate the output port which will be used later for packet transmission)
111 and then finally returning the packets back to the distributor thread.
113 The distributor thread will then call the distributor api
114 ``rte_distributor_returned_pkts()`` to get the processed packets, and will enqueue
115 them to another rte_ring for transfer to the TX thread for transmission on the
116 output port. The transmit thread will dequeue the packets from the ring and
117 transmit them on the output port specified in packet mbuf.
119 Users who wish to terminate the running of the application have to press ctrl+C
120 (or send SIGINT to the app). Upon this signal, a signal handler provided
121 in the application will terminate all running threads gracefully and print
122 final statistics to the user.
126 .. figure:: img/dist_app.*
128 Distributor Sample Application Layout
131 Debug Logging Support
132 ---------------------
134 Debug logging is provided as part of the application; the user needs to uncomment
135 the line "#define DEBUG" defined in start of the application in main.c to enable debug logs.
140 The main function will print statistics on the console every second. These
141 statistics include the number of packets enqueued and dequeued at each stage
142 in the application, and also key statistics per worker, including how many
143 packets of each burst size (1-8) were sent to each worker thread.
145 Application Initialization
146 --------------------------
148 Command line parsing is done in the same way as it is done in the L2 Forwarding Sample
149 Application. See :ref:`l2_fwd_app_cmd_arguments`.
151 Mbuf pool initialization is done in the same way as it is done in the L2 Forwarding
152 Sample Application. See :ref:`l2_fwd_app_mbuf_init`.
154 Driver Initialization is done in same way as it is done in the L2 Forwarding Sample
155 Application. See :ref:`l2_fwd_app_dvr_init`.
157 RX queue initialization is done in the same way as it is done in the L2 Forwarding
158 Sample Application. See :ref:`l2_fwd_app_rx_init`.
160 TX queue initialization is done in the same way as it is done in the L2 Forwarding
161 Sample Application. See :ref:`l2_fwd_app_tx_init`.