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diff --git a/doc/guides/linux_gsg/enable_func.rst b/doc/guides/linux_gsg/enable_func.rst new file mode 100644 index 00000000..076770f2 --- /dev/null +++ b/doc/guides/linux_gsg/enable_func.rst @@ -0,0 +1,218 @@ +.. BSD LICENSE + Copyright(c) 2010-2014 Intel Corporation. All rights reserved. + All rights reserved. + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions + are met: + + * Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + * Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in + the documentation and/or other materials provided with the + distribution. + * Neither the name of Intel Corporation nor the names of its + contributors may be used to endorse or promote products derived + from this software without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +.. _Enabling_Additional_Functionality: + +Enabling Additional Functionality +================================= + +.. _High_Precision_Event_Timer: + +High Precision Event Timer HPET) Functionality +---------------------------------------------- + +BIOS Support +~~~~~~~~~~~~ + +The High Precision Timer (HPET) must be enabled in the platform BIOS if the HPET is to be used. +Otherwise, the Time Stamp Counter (TSC) is used by default. +The BIOS is typically accessed by pressing F2 while the platform is starting up. +The user can then navigate to the HPET option. On the Crystal Forest platform BIOS, the path is: +**Advanced -> PCH-IO Configuration -> High Precision Timer ->** (Change from Disabled to Enabled if necessary). + +On a system that has already booted, the following command can be issued to check if HPET is enabled:: + + grep hpet /proc/timer_list + +If no entries are returned, HPET must be enabled in the BIOS (as per the instructions above) and the system rebooted. + +Linux Kernel Support +~~~~~~~~~~~~~~~~~~~~ + +The DPDK makes use of the platform HPET timer by mapping the timer counter into the process address space, and as such, +requires that the ``HPET_MMAP`` kernel configuration option be enabled. + +.. warning:: + + On Fedora, and other common distributions such as Ubuntu, the ``HPET_MMAP`` kernel option is not enabled by default. + To recompile the Linux kernel with this option enabled, please consult the distributions documentation for the relevant instructions. + +Enabling HPET in the DPDK +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +By default, HPET support is disabled in the DPDK build configuration files. +To use HPET, the ``CONFIG_RTE_LIBEAL_USE_HPET`` setting should be changed to ``y``, which will enable the HPET settings at compile time. + +For an application to use the ``rte_get_hpet_cycles()`` and ``rte_get_hpet_hz()`` API calls, +and optionally to make the HPET the default time source for the rte_timer library, +the new ``rte_eal_hpet_init()`` API call should be called at application initialization. +This API call will ensure that the HPET is accessible, returning an error to the application if it is not, +for example, if ``HPET_MMAP`` is not enabled in the kernel. +The application can then determine what action to take, if any, if the HPET is not available at run-time. + +.. note:: + + For applications that require timing APIs, but not the HPET timer specifically, + it is recommended that the ``rte_get_timer_cycles()`` and ``rte_get_timer_hz()`` API calls be used instead of the HPET-specific APIs. + These generic APIs can work with either TSC or HPET time sources, depending on what is requested by an application call to ``rte_eal_hpet_init()``, + if any, and on what is available on the system at runtime. + +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 Linux file system objects should be adjusted to ensure that +the Linux user account being used to run the DPDK application has access to them: + +* All directories which serve as hugepage mount points, for example, ``/mnt/huge`` + +* The userspace-io device files in ``/dev``, for example, ``/dev/uio0``, ``/dev/uio1``, and so on + +* The userspace-io sysfs config and resource files, for example for ``uio0``:: + + /sys/class/uio/uio0/device/config + /sys/class/uio/uio0/device/resource* + +* If the HPET is to be used, ``/dev/hpet`` + +.. note:: + + On some Linux installations, ``/dev/hugepages`` is also a hugepage mount point created by default. + +Power Management and Power Saving Functionality +----------------------------------------------- + +Enhanced Intel SpeedStep® Technology must be enabled in the platform BIOS if the power management feature of DPDK is to be used. +Otherwise, the sys file folder ``/sys/devices/system/cpu/cpu0/cpufreq`` will not exist, and the CPU frequency- based power management cannot be used. +Consult the relevant BIOS documentation to determine how these settings can be accessed. + +For example, on some Intel reference platform BIOS variants, the path to Enhanced Intel SpeedStep® Technology is:: + + Advanced + -> Processor Configuration + -> Enhanced Intel SpeedStep® Tech + +In addition, C3 and C6 should be enabled as well for power management. The path of C3 and C6 on the same platform BIOS is:: + + Advanced + -> Processor Configuration + -> Processor C3 Advanced + -> Processor Configuration + -> Processor C6 + +Using Linux Core Isolation to Reduce Context Switches +----------------------------------------------------- + +While the threads used by an DPDK application are pinned to logical cores on the system, +it is possible for the Linux scheduler to run other tasks on those cores also. +To help prevent additional workloads from running on those cores, +it is possible to use the ``isolcpus`` Linux kernel parameter to isolate them from the general Linux scheduler. + +For example, if DPDK applications are to run on logical cores 2, 4 and 6, +the following should be added to the kernel parameter list: + +.. code-block:: console + + isolcpus=2,4,6 + +Loading the DPDK KNI Kernel Module +---------------------------------- + +To run the DPDK Kernel NIC Interface (KNI) sample application, an extra kernel module (the kni module) must be loaded into the running kernel. +The module is found in the kmod sub-directory of the DPDK target directory. +Similar to the loading of the ``igb_uio`` module, this module should be loaded using the insmod command as shown below +(assuming that the current directory is the DPDK target directory): + +.. code-block:: console + + insmod kmod/rte_kni.ko + +.. note:: + + See the "Kernel NIC Interface Sample Application" chapter in the *DPDK Sample Applications User Guide* for more details. + +Using Linux IOMMU Pass-Through to Run DPDK with Intel® VT-d +----------------------------------------------------------- + +To enable Intel® VT-d in a Linux kernel, a number of kernel configuration options must be set. These include: + +* ``IOMMU_SUPPORT`` + +* ``IOMMU_API`` + +* ``INTEL_IOMMU`` + +In addition, to run the DPDK with Intel® VT-d, the ``iommu=pt`` kernel parameter must be used when using ``igb_uio`` driver. +This results in pass-through of the DMAR (DMA Remapping) lookup in the host. +Also, if ``INTEL_IOMMU_DEFAULT_ON`` is not set in the kernel, the ``intel_iommu=on`` kernel parameter must be used too. +This ensures that the Intel IOMMU is being initialized as expected. + +Please note that while using ``iommu=pt`` is compulsory for ``igb_uio driver``, the ``vfio-pci`` driver can actually work with both ``iommu=pt`` and ``iommu=on``. + +High Performance of Small Packets on 40G NIC +-------------------------------------------- + +As there might be firmware fixes for performance enhancement in latest version +of firmware image, the firmware update might be needed for getting high performance. +Check with the local Intel's Network Division application engineers for firmware updates. +The base driver to support firmware version of FVL3E will be integrated in the next +DPDK release, so currently the validated firmware version is 4.2.6. + +Enabling Extended Tag +~~~~~~~~~~~~~~~~~~~~~ + +PCI configuration of ``extended_tag`` has big impact on small packet size +performance of 40G ports. Enabling ``extended_tag`` can help 40G port to +achieve the best performance, especially for small packet size. + +* Disabling/enabling ``extended_tag`` can be done in some BIOS implementations. + +* If BIOS does not enable it, and does not support changing it, tools + (e.g. ``setpci`` on Linux) can be used to enable or disable ``extended_tag``. + +* From release 16.04, ``extended_tag`` is enabled by default during port + initialization, users don't need to care about that anymore. + +Use 16 Bytes RX Descriptor Size +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +As i40e PMD supports both 16 and 32 bytes RX descriptor sizes, and 16 bytes size can provide helps to high performance of small packets. +Configuration of ``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC`` in config files can be changed to use 16 bytes size RX descriptors. + +High Performance and per Packet Latency Tradeoff +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Due to the hardware design, the interrupt signal inside NIC is needed for per +packet descriptor write-back. The minimum interval of interrupts could be set +at compile time by ``CONFIG_RTE_LIBRTE_I40E_ITR_INTERVAL`` in configuration files. +Though there is a default configuration, the interval could be tuned by the +users with that configuration item depends on what the user cares about more, +performance or per packet latency. |