dist_app.rst revision 97f17497
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30
31Distributor Sample Application
32==============================
33
34The distributor sample application is a simple example of packet distribution
35to cores using the Data Plane Development Kit (DPDK).
36
37Overview
38--------
39
40The distributor application performs the distribution of packets that are received
41on an RX_PORT to different cores. When processed by the cores, the destination
42port of a packet is the port from the enabled port mask adjacent to the one on
43which 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
45into each other.
46
47This application can be used to benchmark performance using the traffic
48generator as shown in the figure below.
49
50.. _figure_dist_perf:
51
52.. figure:: img/dist_perf.*
53
54   Performance Benchmarking Setup (Basic Environment)
55
56
57Compiling the Application
58-------------------------
59
60#.  Go to the sample application directory:
61
62    ..  code-block:: console
63
64        export RTE_SDK=/path/to/rte_sdk
65        cd ${RTE_SDK}/examples/distributor
66
67#.  Set the target (a default target is used if not specified). For example:
68
69    ..  code-block:: console
70
71        export RTE_TARGET=x86_64-native-linuxapp-gcc
72
73    See the DPDK Getting Started Guide for possible RTE_TARGET values.
74
75#.  Build the application:
76
77    ..  code-block:: console
78
79        make
80
81Running the Application
82-----------------------
83
84#. The application has a number of command line options:
85
86   ..  code-block:: console
87
88       ./build/distributor_app [EAL options] -- -p PORTMASK
89
90   where,
91
92   *   -p PORTMASK: Hexadecimal bitmask of ports to configure
93
94#. To run the application in linuxapp environment with 10 lcores, 4 ports,
95   issue the command:
96
97   ..  code-block:: console
98
99       $ ./build/distributor_app -c 0x4003fe -n 4 -- -p f
100
101#. Refer to the DPDK Getting Started Guide for general information on running
102   applications and the Environment Abstraction Layer (EAL) options.
103
104Explanation
105-----------
106
107The distributor application consists of three types of threads: a receive
108thread (lcore_rx()), a set of worker threads(lcore_worker())
109and a transmit thread(lcore_tx()). How these threads work together is shown
110in :numref:`figure_dist_app` below. The main() function launches  threads of these three types.
111Each thread has a while loop which will be doing processing and which is
112terminated only upon SIGINT or ctrl+C. The receive and transmit threads
113communicate using a software ring (rte_ring structure).
114
115The receive thread receives the packets using rte_eth_rx_burst() and gives
116them to  the distributor (using rte_distributor_process() API) which will
117be called in context of the receive thread itself. The distributor distributes
118the packets to workers threads based on the tagging of the packet -
119indicated by the hash field in the mbuf. For IP traffic, this field is
120automatically filled by the NIC with the "usr" hash value for the packet,
121which works as a per-flow tag.
122
123More than one worker thread can exist as part of the application, and these
124worker threads do simple packet processing by requesting packets from
125the distributor, doing a simple XOR operation on the input port mbuf field
126(to indicate the output port which will be used later for packet transmission)
127and then finally returning the packets back to the distributor in the RX thread.
128
129Meanwhile, the receive thread will call the distributor api
130rte_distributor_returned_pkts() to get the packets processed, and will enqueue
131them to a ring for transfer to the TX thread for transmission on the output port.
132The transmit thread will dequeue the packets from the ring and transmit them on
133the output port specified in packet mbuf.
134
135Users who wish to terminate the running of the application have to press ctrl+C
136(or send SIGINT to the app). Upon this signal, a signal handler provided
137in the application will terminate all running threads gracefully and print
138final statistics to the user.
139
140.. _figure_dist_app:
141
142.. figure:: img/dist_app.*
143
144   Distributor Sample Application Layout
145
146
147Debug Logging Support
148---------------------
149
150Debug logging is provided as part of the application; the user needs to uncomment
151the line "#define DEBUG" defined in start of the application in main.c to enable debug logs.
152
153Statistics
154----------
155
156Upon SIGINT (or) ctrl+C, the print_stats() function displays the count of packets
157processed at the different stages in the application.
158
159Application Initialization
160--------------------------
161
162Command line parsing is done in the same way as it is done in the L2 Forwarding Sample
163Application. See :ref:`l2_fwd_app_cmd_arguments`.
164
165Mbuf pool initialization is done in the same way as it is done in the L2 Forwarding
166Sample Application. See :ref:`l2_fwd_app_mbuf_init`.
167
168Driver Initialization is done in same way as it is done in the L2 Forwarding Sample
169Application. See :ref:`l2_fwd_app_dvr_init`.
170
171RX queue initialization is done in the same way as it is done in the L2 Forwarding
172Sample Application. See :ref:`l2_fwd_app_rx_init`.
173
174TX queue initialization is done in the same way as it is done in the L2 Forwarding
175Sample Application. See :ref:`l2_fwd_app_tx_init`.
176