1.. BSD LICENSE 2 Copyright(c) 2010-2014 Intel Corporation. All rights reserved. 3 All rights reserved. 4 5 Redistribution and use in source and binary forms, with or without 6 modification, are permitted provided that the following conditions 7 are met: 8 9 * Redistributions of source code must retain the above copyright 10 notice, this list of conditions and the following disclaimer. 11 * Redistributions in binary form must reproduce the above copyright 12 notice, this list of conditions and the following disclaimer in 13 the documentation and/or other materials provided with the 14 distribution. 15 * Neither the name of Intel Corporation nor the names of its 16 contributors may be used to endorse or promote products derived 17 from this software without specific prior written permission. 18 19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31.. _Enabling_Additional_Functionality: 32 33Enabling Additional Functionality 34================================= 35 36.. _High_Precision_Event_Timer: 37 38High Precision Event Timer (HPET) Functionality 39----------------------------------------------- 40 41BIOS Support 42~~~~~~~~~~~~ 43 44The High Precision Timer (HPET) must be enabled in the platform BIOS if the HPET is to be used. 45Otherwise, the Time Stamp Counter (TSC) is used by default. 46The BIOS is typically accessed by pressing F2 while the platform is starting up. 47The user can then navigate to the HPET option. On the Crystal Forest platform BIOS, the path is: 48**Advanced -> PCH-IO Configuration -> High Precision Timer ->** (Change from Disabled to Enabled if necessary). 49 50On a system that has already booted, the following command can be issued to check if HPET is enabled:: 51 52 grep hpet /proc/timer_list 53 54If no entries are returned, HPET must be enabled in the BIOS (as per the instructions above) and the system rebooted. 55 56Linux Kernel Support 57~~~~~~~~~~~~~~~~~~~~ 58 59The DPDK makes use of the platform HPET timer by mapping the timer counter into the process address space, and as such, 60requires that the ``HPET_MMAP`` kernel configuration option be enabled. 61 62.. warning:: 63 64 On Fedora, and other common distributions such as Ubuntu, the ``HPET_MMAP`` kernel option is not enabled by default. 65 To recompile the Linux kernel with this option enabled, please consult the distributions documentation for the relevant instructions. 66 67Enabling HPET in the DPDK 68~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 69 70By default, HPET support is disabled in the DPDK build configuration files. 71To use HPET, the ``CONFIG_RTE_LIBEAL_USE_HPET`` setting should be changed to ``y``, which will enable the HPET settings at compile time. 72 73For an application to use the ``rte_get_hpet_cycles()`` and ``rte_get_hpet_hz()`` API calls, 74and optionally to make the HPET the default time source for the rte_timer library, 75the new ``rte_eal_hpet_init()`` API call should be called at application initialization. 76This API call will ensure that the HPET is accessible, returning an error to the application if it is not, 77for example, if ``HPET_MMAP`` is not enabled in the kernel. 78The application can then determine what action to take, if any, if the HPET is not available at run-time. 79 80.. note:: 81 82 For applications that require timing APIs, but not the HPET timer specifically, 83 it is recommended that the ``rte_get_timer_cycles()`` and ``rte_get_timer_hz()`` API calls be used instead of the HPET-specific APIs. 84 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()``, 85 if any, and on what is available on the system at runtime. 86 87Running DPDK Applications Without Root Privileges 88-------------------------------------------------------- 89 90.. note:: 91 92 The instructions below will allow running DPDK as non-root with older 93 Linux kernel versions. However, since version 4.0, the kernel does not allow 94 unprivileged processes to read the physical address information from 95 the pagemaps file, making it impossible for those processes to use HW 96 devices which require physical addresses 97 98Although applications using the DPDK use network ports and other hardware resources directly, 99with a number of small permission adjustments it is possible to run these applications as a user other than "root". 100To do so, the ownership, or permissions, on the following Linux file system objects should be adjusted to ensure that 101the Linux user account being used to run the DPDK application has access to them: 102 103* All directories which serve as hugepage mount points, for example, ``/mnt/huge`` 104 105* The userspace-io device files in ``/dev``, for example, ``/dev/uio0``, ``/dev/uio1``, and so on 106 107* The userspace-io sysfs config and resource files, for example for ``uio0``:: 108 109 /sys/class/uio/uio0/device/config 110 /sys/class/uio/uio0/device/resource* 111 112* If the HPET is to be used, ``/dev/hpet`` 113 114.. note:: 115 116 On some Linux installations, ``/dev/hugepages`` is also a hugepage mount point created by default. 117 118Power Management and Power Saving Functionality 119----------------------------------------------- 120 121Enhanced Intel SpeedStep® Technology must be enabled in the platform BIOS if the power management feature of DPDK is to be used. 122Otherwise, the sys file folder ``/sys/devices/system/cpu/cpu0/cpufreq`` will not exist, and the CPU frequency- based power management cannot be used. 123Consult the relevant BIOS documentation to determine how these settings can be accessed. 124 125For example, on some Intel reference platform BIOS variants, the path to Enhanced Intel SpeedStep® Technology is:: 126 127 Advanced 128 -> Processor Configuration 129 -> Enhanced Intel SpeedStep® Tech 130 131In addition, C3 and C6 should be enabled as well for power management. The path of C3 and C6 on the same platform BIOS is:: 132 133 Advanced 134 -> Processor Configuration 135 -> Processor C3 Advanced 136 -> Processor Configuration 137 -> Processor C6 138 139Using Linux Core Isolation to Reduce Context Switches 140----------------------------------------------------- 141 142While the threads used by an DPDK application are pinned to logical cores on the system, 143it is possible for the Linux scheduler to run other tasks on those cores also. 144To help prevent additional workloads from running on those cores, 145it is possible to use the ``isolcpus`` Linux kernel parameter to isolate them from the general Linux scheduler. 146 147For example, if DPDK applications are to run on logical cores 2, 4 and 6, 148the following should be added to the kernel parameter list: 149 150.. code-block:: console 151 152 isolcpus=2,4,6 153 154Loading the DPDK KNI Kernel Module 155---------------------------------- 156 157To run the DPDK Kernel NIC Interface (KNI) sample application, an extra kernel module (the kni module) must be loaded into the running kernel. 158The module is found in the kmod sub-directory of the DPDK target directory. 159Similar to the loading of the ``igb_uio`` module, this module should be loaded using the insmod command as shown below 160(assuming that the current directory is the DPDK target directory): 161 162.. code-block:: console 163 164 insmod kmod/rte_kni.ko 165 166.. note:: 167 168 See the "Kernel NIC Interface Sample Application" chapter in the *DPDK Sample Applications User Guide* for more details. 169 170Using Linux IOMMU Pass-Through to Run DPDK with Intel® VT-d 171----------------------------------------------------------- 172 173To enable Intel® VT-d in a Linux kernel, a number of kernel configuration options must be set. These include: 174 175* ``IOMMU_SUPPORT`` 176 177* ``IOMMU_API`` 178 179* ``INTEL_IOMMU`` 180 181In addition, to run the DPDK with Intel® VT-d, the ``iommu=pt`` kernel parameter must be used when using ``igb_uio`` driver. 182This results in pass-through of the DMAR (DMA Remapping) lookup in the host. 183Also, if ``INTEL_IOMMU_DEFAULT_ON`` is not set in the kernel, the ``intel_iommu=on`` kernel parameter must be used too. 184This ensures that the Intel IOMMU is being initialized as expected. 185 186Please 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``. 187