f2fc83b40f
There is a common macro __rte_unused, avoiding warnings, which is now used where appropriate for consistency. Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
95 lines
2.5 KiB
ReStructuredText
95 lines
2.5 KiB
ReStructuredText
.. SPDX-License-Identifier: BSD-3-Clause
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Copyright(c) 2010-2014 Intel Corporation.
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Hello World Sample Application
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==============================
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The Hello World sample application is an example of the simplest DPDK application that can be written.
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The application simply prints an "helloworld" message on every enabled lcore.
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Compiling the Application
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-------------------------
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To compile the sample application see :doc:`compiling`.
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The application is located in the ``helloworld`` sub-directory.
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Running the Application
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-----------------------
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To run the example in a linux environment:
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.. code-block:: console
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$ ./build/helloworld -l 0-3 -n 4
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Refer to *DPDK Getting Started Guide* for general information on running applications
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and the Environment Abstraction Layer (EAL) options.
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Explanation
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-----------
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The following sections provide some explanation of code.
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EAL Initialization
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~~~~~~~~~~~~~~~~~~
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The first task is to initialize the Environment Abstraction Layer (EAL).
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This is done in the main() function using the following code:
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.. code-block:: c
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int
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main(int argc, char **argv)
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{
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ret = rte_eal_init(argc, argv);
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if (ret < 0)
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rte_panic("Cannot init EAL\n");
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This call finishes the initialization process that was started before main() is called (in case of a Linux environment).
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The argc and argv arguments are provided to the rte_eal_init() function.
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The value returned is the number of parsed arguments.
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Starting Application Unit Lcores
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Once the EAL is initialized, the application is ready to launch a function on an lcore.
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In this example, lcore_hello() is called on every available lcore.
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The following is the definition of the function:
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.. code-block:: c
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static int
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lcore_hello(__rte_unused void *arg)
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{
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unsigned lcore_id;
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lcore_id = rte_lcore_id();
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printf("hello from core %u\n", lcore_id);
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return 0;
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}
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The code that launches the function on each lcore is as follows:
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.. code-block:: c
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/* call lcore_hello() on every slave lcore */
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RTE_LCORE_FOREACH_SLAVE(lcore_id) {
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rte_eal_remote_launch(lcore_hello, NULL, lcore_id);
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}
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/* call it on master lcore too */
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lcore_hello(NULL);
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The following code is equivalent and simpler:
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.. code-block:: c
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rte_eal_mp_remote_launch(lcore_hello, NULL, CALL_MASTER);
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Refer to the *DPDK API Reference* for detailed information on the rte_eal_mp_remote_launch() function.
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