xref: /dpdk/doc/guides/linux_gsg/build_sample_apps.rst (revision 8205e241b2b01c05f2cffe5158c053d614d1f68c)
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30
31Compiling and Running Sample Applications
32=========================================
33
34The chapter describes how to compile and run applications in an DPDK environment.
35It also provides a pointer to where sample applications are stored.
36
37.. note::
38
39    Parts of this process can also be done using the setup script described in **Chapter 6** of this document.
40
41Compiling a Sample Application
42------------------------------
43
44Once an DPDK target environment directory has been created (such as x86_64-native-linuxapp-gcc),
45it contains all libraries and header files required to build an application.
46
47When compiling an application in the Linux* environment on the DPDK, the following variables must be exported:
48
49* RTE_SDK - Points to the DPDK installation directory.
50
51* RTE_TARGET - Points to the DPDK target environment directory.
52
53The following is an example of creating the helloworld application, which runs in the DPDK Linux environment.
54This example may be found in the ${RTE_SDK}/examples directory.
55
56The directory contains the main.c file. This file, when combined with the libraries in the DPDK target environment,
57calls the various functions to initialize the DPDK environment,
58then launches an entry point (dispatch application) for each core to be utilized.
59By default, the binary is generated in the build directory.
60
61.. code-block:: console
62
63    user@host:~/DPDK$ cd examples/helloworld/
64    user@host:~/DPDK/examples/helloworld$ export RTE_SDK=$HOME/DPDK
65    user@host:~/DPDK/examples/helloworld$ export RTE_TARGET=x86_64-native-linuxapp-gcc
66    user@host:~/DPDK/examples/helloworld$ make
67        CC main.o
68        LD helloworld
69        INSTALL-APP helloworld
70        INSTALL-MAP helloworld.map
71
72    user@host:~/DPDK/examples/helloworld$ ls build/app
73        helloworld helloworld.map
74
75.. note::
76
77    In the above example, helloworld was in the directory structure of the DPDK.
78    However, it could have been located outside the directory structure to keep the DPDK structure intact.
79    In the following case, the helloworld application is copied to a new directory as a new starting point.
80
81    .. code-block:: console
82
83            user@host:~$ export RTE_SDK=/home/user/DPDK
84            user@host:~$ cp -r $(RTE_SDK)/examples/helloworld my_rte_app
85            user@host:~$ cd my_rte_app/
86            user@host:~$ export RTE_TARGET=x86_64-native-linuxapp-gcc
87            user@host:~/my_rte_app$ make
88                CC main.o
89                LD helloworld
90                INSTALL-APP helloworld
91                INSTALL-MAP helloworld.map
92
93Running a Sample Application
94----------------------------
95
96.. warning::
97
98    The UIO drivers and hugepages must be setup prior to running an application.
99
100.. warning::
101
102    Any ports to be used by the application must be already bound to an appropriate kernel
103    module, as described in Section 3.5, prior to running the application.
104
105The application is linked with the DPDK target environment's Environmental Abstraction Layer (EAL) library,
106which provides some options that are generic to every DPDK application.
107
108The following is the list of options that can be given to the EAL:
109
110.. code-block:: console
111
112    ./rte-app -n NUM [-c COREMASK] [-b <domain:bus:devid.func>] [--socket-mem=MB,...] [-m MB] [-r NUM] [-v] [--file-prefix] [--proc-type <primary|secondary|auto>] [-- xen-dom0]
113
114The EAL options are as follows:
115
116*   -c COREMASK: An hexadecimal bit mask of the cores to run on. Note that core numbering can change between platforms and should be determined beforehand.
117
118*   -n NUM: Number of memory channels per processor socket
119
120*   -b <domain:bus:devid.func>: blacklisting of ports; prevent EAL from using specified PCI device (multiple -b options are allowed)
121
122*   --use-device: use the specified Ethernet device(s) only. Use comma-separate <[domain:]bus:devid.func> values. Cannot be used with -b option
123
124*   --socket-mem: Memory to allocate from hugepages on specific sockets
125
126*   -m MB: Memory to allocate from hugepages, regardless of processor socket. It is recommended that --socket-mem be used instead of this option.
127
128*   -r NUM: Number of memory ranks
129
130*   -v: Display version information on startup
131
132*   --huge-dir: The directory where hugetlbfs is mounted
133
134*   --file-prefix: The prefix text used for hugepage filenames
135
136*   --proc-type: The type of process instance
137
138*   --xen-dom0: Support application running on Xen Domain0 without hugetlbfs
139
140*   --vmware-tsc-map: use VMware TSC map instead of native RDTSC
141
142*   --base-virtaddr: specify base virtual address
143
144*   --vfio-intr: specify interrupt type to be used by VFIO (has no effect if VFIO is not used)
145
146The -c and the -n options are mandatory; the others are optional.
147
148Copy the DPDK application binary to your target, then run the application as follows
149(assuming the platform has four memory channels per processor socket,
150and that cores 0-3 are present and are to be used for running the application):
151
152.. code-block:: console
153
154    user@target:~$ ./helloworld -c f -n 4
155
156.. note::
157
158    The --proc-type and  --file-prefix EAL options are used for running multiple DPDK processes.
159    See the “Multi-process Sample Application” chapter in the *DPDK Sample Applications User Guide* and
160    the *DPDK Programmers Guide* for more details.
161
162Logical Core Use by Applications
163~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
164
165The coremask parameter is always mandatory for DPDK applications.
166Each bit of the mask corresponds to the equivalent logical core number as reported by Linux.
167Since these logical core numbers, and their mapping to specific cores on specific NUMA sockets, can vary from platform to platform,
168it is recommended that the core layout for each platform be considered when choosing the coremask to use in each case.
169
170On initialization of the EAL layer by an DPDK application, the logical cores to be used and their socket location are displayed.
171This information can also be determined for all cores on the system by examining the /proc/cpuinfo file, for example, by running cat /proc/cpuinfo.
172The physical id attribute listed for each processor indicates the CPU socket to which it belongs.
173This can be useful when using other processors to understand the mapping of the logical cores to the sockets.
174
175.. note::
176
177    A more graphical view of the logical core layout may be obtained using the lstopo Linux utility.
178    On Fedora* Linux, this may be installed and run using the following command:
179
180.. code-block:: console
181
182        sudo yum install hwloc
183        ./lstopo
184
185.. warning::
186
187    The logical core layout can change between different board layouts and should be checked before selecting an application coremask.
188
189Hugepage Memory Use by Applications
190~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
191
192When running an application, it is recommended to use the same amount of memory as that allocated for hugepages.
193This is done automatically by the DPDK application at startup,
194if no -m or --socket-mem parameter is passed to it when run.
195
196If more memory is requested by explicitly passing a -m or --socket-mem value, the application fails.
197However, the application itself can also fail if the user requests less memory than the reserved amount of hugepage-memory, particularly if using the -m option.
198The reason is as follows.
199Suppose the system has 1024 reserved 2 MB pages in socket 0 and 1024 in socket 1.
200If the user requests 128 MB of memory, the 64 pages may not match the constraints:
201
202*   The hugepage memory by be given to the application by the kernel in socket 1 only.
203    In this case, if the application attempts to create an object, such as a ring or memory pool in socket 0, it fails.
204    To avoid this issue, it is recommended that the -- socket-mem option be used instead of the -m option.
205
206*   These pages can be located anywhere in physical memory, and, although the DPDK EAL will attempt to allocate memory in contiguous blocks,
207    it is possible that the pages will not be contiguous. In this case, the application is not able to allocate big memory pools.
208
209The socket-mem option can be used to request specific amounts of memory for specific sockets.
210This is accomplished by supplying the --socket-mem flag followed by amounts of memory requested on each socket,
211for example, supply --socket-mem=0,512 to try and reserve 512 MB for socket 1 only.
212Similarly, on a four socket system, to allocate 1 GB memory on each of sockets 0 and 2 only, the parameter --socket-mem=1024,0,1024 can be used.
213No memory will be reserved on any CPU socket that is not explicitly referenced, for example, socket 3 in this case.
214If the DPDK cannot allocate enough memory on each socket, the EAL initialization fails.
215
216Additional Sample Applications
217------------------------------
218
219Additional sample applications are included in the ${RTE_SDK}/examples directory.
220These sample applications may be built and run in a manner similar to that described in earlier sections in this manual.
221In addition, see the *DPDK Sample Applications User Guide* for a description of the application,
222specific instructions on compilation and execution and some explanation of the code.
223
224Additional Test Applications
225----------------------------
226
227In addition, there are two other applications that are built when the libraries are created.
228The source files for these are in the DPDK/app directory and are called test and testpmd.
229Once the libraries are created, they can be found in the build/app directory.
230
231*   The test application provides a variety of specific tests for the various functions in the DPDK.
232
233*   The testpmd application provides a number of different packet throughput tests and
234    examples of features such as how to use the Flow Director found in the Intel® 82599 10 Gigabit Ethernet Controller.
235