The coremask (-c 0x0f) or corelist (-l 0-3) parameter is always mandatory for DPDK applications.
Each bit of the mask corresponds to the equivalent logical core number as reported by Linux. The preferred corelist option is a cleaner method to define cores to be used.
On initialization of the EAL layer by an DPDK application, the logical cores to be used and their socket location are displayed.
This information can also be determined for all cores on the system by examining the ``/proc/cpuinfo`` file, for example, by running cat ``/proc/cpuinfo``.
The physical id attribute listed for each processor indicates the CPU socket to which it belongs.
This can be useful when using other processors to understand the mapping of the logical cores to the sockets.
..note::
A more graphical view of the logical core layout may be obtained using the ``lstopo`` Linux utility.
On Fedora Linux, this may be installed and run using the following command::
When running an application, it is recommended to use the same amount of memory as that allocated for hugepages.
This is done automatically by the DPDK application at startup,
if no ``-m`` or ``--socket-mem`` parameter is passed to it when run.
If more memory is requested by explicitly passing a ``-m`` or ``--socket-mem`` value, the application fails.
However, 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.
The reason is as follows.
Suppose the system has 1024 reserved 2 MB pages in socket 0 and 1024 in socket 1.
If the user requests 128 MB of memory, the 64 pages may not match the constraints:
* The hugepage memory by be given to the application by the kernel in socket 1 only.
In this case, if the application attempts to create an object, such as a ring or memory pool in socket 0, it fails.
To avoid this issue, it is recommended that the ``--socket-mem`` option be used instead of the ``-m`` option.
* These pages can be located anywhere in physical memory, and, although the DPDK EAL will attempt to allocate memory in contiguous blocks,
it is possible that the pages will not be contiguous. In this case, the application is not able to allocate big memory pools.
The socket-mem option can be used to request specific amounts of memory for specific sockets.
This is accomplished by supplying the ``--socket-mem`` flag followed by amounts of memory requested on each socket,
for example, supply ``--socket-mem=0,512`` to try and reserve 512 MB for socket 1 only.
Similarly, 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.
No memory will be reserved on any CPU socket that is not explicitly referenced, for example, socket 3 in this case.
If the DPDK cannot allocate enough memory on each socket, the EAL initialization fails.
Additional Sample Applications
------------------------------
Additional sample applications are included in the ${RTE_SDK}/examples directory.
These sample applications may be built and run in a manner similar to that described in earlier sections in this manual.
In addition, see the *DPDK Sample Applications User Guide* for a description of the application,
specific instructions on compilation and execution and some explanation of the code.
Additional Test Applications
----------------------------
In addition, there are two other applications that are built when the libraries are created.
The source files for these are in the DPDK/app directory and are called test and testpmd.
Once the libraries are created, they can be found in the build/app directory.
* The test application provides a variety of specific tests for the various functions in the DPDK.
* The testpmd application provides a number of different packet throughput tests and
examples of features such as how to use the Flow Director found in the Intel® 82599 10 Gigabit Ethernet Controller.
