3. Compiling the DPDK Target from Source

3.1. System Requirements

The DPDK and its applications require the GNU make system (gmake) to build on FreeBSD. Optionally, gcc may also be used in place of clang to build the DPDK, in which case it too must be installed prior to compiling the DPDK. The installation of these tools is covered in this section.

Compiling the DPDK requires the FreeBSD kernel sources, which should be included during the installation of FreeBSD on the development platform. The DPDK also requires the use of FreeBSD ports to compile and function.

To use the FreeBSD ports system, it is required to update and extract the FreeBSD ports tree by issuing the following commands:

portsnap fetch
portsnap extract

If the environment requires proxies for external communication, these can be set using:

setenv http_proxy <my_proxy_host>:<port>
setenv ftp_proxy <my_proxy_host>:<port>

The FreeBSD ports below need to be installed prior to building the DPDK. In general these can be installed using the following set of commands:

cd /usr/ports/<port_location>

make config-recursive

make install

make clean

Each port location can be found using:

whereis <port_name>

The ports required and their locations are as follows:

  • dialog4ports: /usr/ports/ports-mgmt/dialog4ports
  • GNU make(gmake): /usr/ports/devel/gmake
  • coreutils: /usr/ports/sysutils/coreutils

For compiling and using the DPDK with gcc, the compiler must be installed from the ports collection:

  • gcc: version 4.9 is recommended /usr/ports/lang/gcc49. Ensure that CPU_OPTS is selected (default is OFF).

When running the make config-recursive command, a dialog may be presented to the user. For the installation of the DPDK, the default options were used.

Note

To avoid multiple dialogs being presented to the user during make install, it is advisable before running the make install command to re-run the make config-recursive command until no more dialogs are seen.

3.2. Install the DPDK and Browse Sources

First, uncompress the archive and move to the DPDK source directory:

unzip DPDK-<version>.zip
cd DPDK-<version>

The DPDK is composed of several directories:

  • lib: Source code of DPDK libraries
  • app: Source code of DPDK applications (automatic tests)
  • examples: Source code of DPDK applications
  • config, tools, scripts, mk: Framework-related makefiles, scripts and configuration

3.3. Installation of the DPDK Target Environments

The format of a DPDK target is:

ARCH-MACHINE-EXECENV-TOOLCHAIN

Where:

  • ARCH is: x86_64
  • MACHINE is: native
  • EXECENV is: bsdapp
  • TOOLCHAIN is: gcc | clang

The configuration files for the DPDK targets can be found in the DPDK/config directory in the form of:

defconfig_ARCH-MACHINE-EXECENV-TOOLCHAIN

Note

Configuration files are provided with the RTE_MACHINE optimization level set. Within the configuration files, the RTE_MACHINE configuration value is set to native, which means that the compiled software is tuned for the platform on which it is built. For more information on this setting, and its possible values, see the DPDK Programmers Guide.

To make the target, use gmake install T=<target>.

For example to compile for FreeBSD use:

gmake install T=x86_64-native-bsdapp-clang

Note

If the compiler binary to be used does not correspond to that given in the TOOLCHAIN part of the target, the compiler command may need to be explicitly specified. For example, if compiling for gcc, where the gcc binary is called gcc4.9, the command would need to be gmake install T=<target> CC=gcc4.9.

3.4. Browsing the Installed DPDK Environment Target

Once a target is created, it contains all the libraries and header files for the DPDK environment that are required to build customer applications. In addition, the test and testpmd applications are built under the build/app directory, which may be used for testing. A kmod directory is also present that contains the kernel modules to install.

3.5. Loading the DPDK contigmem Module

To run a DPDK application, physically contiguous memory is required. In the absence of non-transparent superpages, the included sources for the contigmem kernel module provides the ability to present contiguous blocks of memory for the DPDK to use. The contigmem module must be loaded into the running kernel before any DPDK is run. The module is found in the kmod sub-directory of the DPDK target directory.

The amount of physically contiguous memory along with the number of physically contiguous blocks to be reserved by the module can be set at runtime prior to module loading using:

kenv hw.contigmem.num_buffers=n
kenv hw.contigmem.buffer_size=m

The kernel environment variables can also be specified during boot by placing the following in /boot/loader.conf:

hw.contigmem.num_buffers=n hw.contigmem.buffer_size=m

The variables can be inspected using the following command:

sysctl -a hw.contigmem

Where n is the number of blocks and m is the size in bytes of each area of contiguous memory. A default of two buffers of size 1073741824 bytes (1 Gigabyte) each is set during module load if they are not specified in the environment.

The module can then be loaded using kldload (assuming that the current directory is the DPDK target directory):

kldload ./kmod/contigmem.ko

It is advisable to include the loading of the contigmem module during the boot process to avoid issues with potential memory fragmentation during later system up time. This can be achieved by copying the module to the /boot/kernel/ directory and placing the following into /boot/loader.conf:

contigmem_load="YES"

Note

The contigmem_load directive should be placed after any definitions of hw.contigmem.num_buffers and hw.contigmem.buffer_size if the default values are not to be used.

An error such as:

kldload: can't load ./x86_64-native-bsdapp-gcc/kmod/contigmem.ko:
         Exec format error

is generally attributed to not having enough contiguous memory available and can be verified via dmesg or /var/log/messages:

kernel: contigmalloc failed for buffer <n>

To avoid this error, reduce the number of buffers or the buffer size.

3.6. Loading the DPDK nic_uio Module

After loading the contigmem module, the nic_uio module must also be loaded into the running kernel prior to running any DPDK application. This module must be loaded using the kldload command as shown below (assuming that the current directory is the DPDK target directory).

kldload ./kmod/nic_uio.ko

Note

If the ports to be used are currently bound to a existing kernel driver then the hw.nic_uio.bdfs sysctl value will need to be set before loading the module. Setting this value is described in the next section below.

Currently loaded modules can be seen by using the kldstat command and a module can be removed from the running kernel by using kldunload <module_name>.

To load the module during boot, copy the nic_uio module to /boot/kernel and place the following into /boot/loader.conf:

nic_uio_load="YES"

Note

nic_uio_load="YES" must appear after the contigmem_load directive, if it exists.

By default, the nic_uio module will take ownership of network ports if they are recognized DPDK devices and are not owned by another module. However, since the FreeBSD kernel includes support, either built-in, or via a separate driver module, for most network card devices, it is likely that the ports to be used are already bound to a driver other than nic_uio. The following sub-section describe how to query and modify the device ownership of the ports to be used by DPDK applications.

3.6.1. Binding Network Ports to the nic_uio Module

Device ownership can be viewed using the pciconf -l command. The example below shows four Intel® 82599 network ports under if_ixgbe module ownership.

pciconf -l
ix0@pci0:1:0:0: class=0x020000 card=0x00038086 chip=0x10fb8086 rev=0x01 hdr=0x00
ix1@pci0:1:0:1: class=0x020000 card=0x00038086 chip=0x10fb8086 rev=0x01 hdr=0x00
ix2@pci0:2:0:0: class=0x020000 card=0x00038086 chip=0x10fb8086 rev=0x01 hdr=0x00
ix3@pci0:2:0:1: class=0x020000 card=0x00038086 chip=0x10fb8086 rev=0x01 hdr=0x00

The first column constitutes three components:

  1. Device name: ixN
  2. Unit name: pci0
  3. Selector (Bus:Device:Function): 1:0:0

Where no driver is associated with a device, the device name will be none.

By default, the FreeBSD kernel will include built-in drivers for the most common devices; a kernel rebuild would normally be required to either remove the drivers or configure them as loadable modules.

To avoid building a custom kernel, the nic_uio module can detach a network port from its current device driver. This is achieved by setting the hw.nic_uio.bdfs kernel environment variable prior to loading nic_uio, as follows:

hw.nic_uio.bdfs="b:d:f,b:d:f,..."

Where a comma separated list of selectors is set, the list must not contain any whitespace.

For example to re-bind ix2@pci0:2:0:0 and ix3@pci0:2:0:1 to the nic_uio module upon loading, use the following command:

kenv hw.nic_uio.bdfs="2:0:0,2:0:1"

The variable can also be specified during boot by placing the following into /boot/loader.conf, before the previously-described nic_uio_load line - as shown:

hw.nic_uio.bdfs="2:0:0,2:0:1"
nic_uio_load="YES"

3.6.2. Binding Network Ports Back to their Original Kernel Driver

If the original driver for a network port has been compiled into the kernel, it is necessary to reboot FreeBSD to restore the original device binding. Before doing so, update or remove the hw.nic_uio.bdfs in /boot/loader.conf.

If rebinding to a driver that is a loadable module, the network port binding can be reset without rebooting. To do so, unload both the target kernel module and the nic_uio module, modify or clear the hw.nic_uio.bdfs kernel environment (kenv) value, and reload the two drivers - first the original kernel driver, and then the nic_uio driver. Note: the latter does not need to be reloaded unless there are ports that are still to be bound to it.

Example commands to perform these steps are shown below:

kldunload nic_uio
kldunload <original_driver>

# To clear the value completely:
kenv -u hw.nic_uio.bdfs

# To update the list of ports to bind:
kenv hw.nic_uio.bdfs="b:d:f,b:d:f,..."

kldload <original_driver>

kldload nic_uio  # optional