4. Compiling and Running Sample Applications

4.1. Compiling a Sample Application

Once a DPDK target environment directory has been created (such as x86_64-native-bsdapp-clang), it contains all libraries and header files required to build an application.

When compiling an application in the FreeBSD environment on the DPDK, the following variables must be exported:

• RTE_SDK - Points to the DPDK installation directory.
• RTE_TARGET - Points to the DPDK target environment directory. For FreeBSD, this is the x86_64-native-bsdapp-clang or x86_64-native-bsdapp-gcc directory.

The following is an example of creating the helloworld application, which runs in the DPDK FreeBSD environment. While the example demonstrates compiling using gcc version 4.9, compiling with clang will be similar, except that the CC= parameter can probably be omitted. The helloworld example may be found in the ${RTE_SDK}/examples directory.

The directory contains the main.c file. This file, when combined with the libraries in the DPDK target environment, calls the various functions to initialize the DPDK environment, then launches an entry point (dispatch application) for each core to be utilized. By default, the binary is generated in the build directory.

setenv RTE_SDK /home/user/DPDK
cd $(RTE_SDK)
cd examples/helloworld/
setenv RTE_SDK $HOME/DPDK
setenv RTE_TARGET x86_64-native-bsdapp-gcc

gmake CC=gcc49
  CC main.o
  LD helloworld
  INSTALL-APP helloworld
  INSTALL-MAP helloworld.map

ls build/app
  helloworld helloworld.map

setenv RTE_SDK /home/user/DPDK
cp -r $(RTE_SDK)/examples/helloworld my_rte_app
cd my_rte_app/
setenv RTE_TARGET x86_64-native-bsdapp-gcc

gmake CC=gcc49
  CC main.o
  LD helloworld
  INSTALL-APP helloworld
  INSTALL-MAP helloworld.map

4.2. Running a Sample Application

1. The contigmem and nic_uio modules must be set up prior to running an application.
2. Any ports to be used by the application must be already bound to the nic_uio module, as described in section Binding Network Ports to the nic_uio Module, prior to running the application. The application is linked with the DPDK target environment’s Environment Abstraction Layer (EAL) library, which provides some options that are generic to every DPDK application.

The following is the list of options that can be given to the EAL:

./rte-app -l CORELIST [-n NUM] [-b <domain:bus:devid.func>] \
          [-r NUM] [-v] [--proc-type <primary|secondary|auto>]

The EAL options for FreeBSD are as follows:

• -c COREMASK or -l CORELIST: A hexadecimal bit mask of the cores to run on. Note that core numbering can change between platforms and should be determined beforehand. The corelist is a list of cores to use instead of a core mask.
• -n NUM: Number of memory channels per processor socket.
• -b <domain:bus:devid.func>: Blacklisting of ports; prevent EAL from using specified PCI device (multiple -b options are allowed).
• --use-device: Use the specified Ethernet device(s) only. Use comma-separate [domain:]bus:devid.func values. Cannot be used with -b option.
• -r NUM: Number of memory ranks.
• -v: Display version information on startup.
• --proc-type: The type of process instance.

Other options, specific to Linux and are not supported under FreeBSD are as follows:

• socket-mem: Memory to allocate from hugepages on specific sockets.
• --huge-dir: The directory where hugetlbfs is mounted.
• --file-prefix: The prefix text used for hugepage filenames.
• -m MB: Memory to allocate from hugepages, regardless of processor socket. It is recommended that --socket-mem be used instead of this option.

The -c or -l option is mandatory; the others are optional.

Copy the DPDK application binary to your target, then run the application as follows (assuming the platform has four memory channels, and that cores 0-3 are present and are to be used for running the application):

./helloworld -l 0-3 -n 4

4.3. Running DPDK Applications Without Root Privileges

Although applications using the DPDK use network ports and other hardware resources directly, with a number of small permission adjustments, it is possible to run these applications as a user other than “root”. To do so, the ownership, or permissions, on the following file system objects should be adjusted to ensure that the user account being used to run the DPDK application has access to them:

• The userspace-io device files in /dev, for example, /dev/uio0, /dev/uio1, and so on
• The userspace contiguous memory device: /dev/contigmem