Ettus Knowledge Base - Recent changes [en]

Getting Started with DPDK and UHD

MichaelDickens — Tue, 08 Sep 2026 12:18:54 GMT

‎UHD DPDK Version Dependencies: add 4.11

Instructions for System Setup and Configuration

Ettus — Fri, 04 Sep 2026 16:16:43 GMT

‎Step 4: Install Dependencies

Getting Started with DPDK and UHD

MichaelDickens — Sun, 30 Aug 2026 20:47:23 GMT

‎Abstract: a little more depth

USRP Host Performance Tuning Tips and Tricks

MichaelDickens — Sun, 30 Aug 2026 19:31:23 GMT

whitespace

Getting Started with DPDK and UHD

MichaelDickens — Sun, 30 Aug 2026 19:01:01 GMT

‎USRPs: more concise pagination

USRP Host Performance Tuning Tips and Tricks

MichaelDickens — Sun, 30 Aug 2026 18:45:40 GMT

‎Disable KPTI Protections for Spectre/Meltdown: tweak note to be consistent with other same notes

Getting Started with DPDK and UHD

MichaelDickens — Sun, 30 Aug 2026 18:33:47 GMT

‎Increasing num_recv_frames

@@ Line 88: / Line 88: @@
 * UHD 4.8 and 4.9 can use any version of DPDK from 18.11 to 24.11
-* UHD 4.10 can use any version of DPDK from 19.11 to 25.11
+* UHD 4.10 and 4.11 can use any version of DPDK from 19.11 to 25.11
 == Installing DPDK ==

@@ Line 61: / Line 61: @@
      sudo apt-get install openssh-server htop tree lshw meld git libfftw3-bin ncurses-bin libncurses6 libncursesw6 net-tools ethtool aptitude screen hwloc inxi wireshark wireshark-doc wireshark-dev tshark build-essential ntp doxygen gnome-disk-utility cpufrequtils libsndfile1-dev
-     sudo apt-get install autoconf automake build-essential ccache cmake cpufrequtils doxygen ethtool g++ git inetutils-tools libboost-all-dev libncurses6 libncurses-dev libusb-1.0-0 libusb-1.0-0-dev libusb-dev python3-dev python3-mako python3-numpy python3-requests python3-scipy python3-setuptools python3-ruamel.yaml
+     sudo apt-get install autoconf automake build-essential ccache cmake cpufrequtils doxygen ethtool g++ git inetutils-tools libboost-all-dev libncurses6 libncurses-dev libusb-1.0-0 libusb-1.0-0-dev libusb-dev python3-dev python3-mako python3-numpy python3-requests python3-scipy python3-setuptools python3-ruamel.yaml libfmt9 libfmt-dev libfmt-doc libspdlog1.12 libspdlog-dev
      sudo apt-get install git cmake g++ libboost-all-dev libgmp-dev swig python3-numpy python3-mako python3-sphinx python3-lxml doxygen libfftw3-dev libsdl1.2-dev libgsl-dev libqwt-qt5-dev libqt5opengl5-dev python3-pyqt5 liblog4cpp5-dev libzmq3-dev python3-yaml python3-click python3-click-plugins python3-zmq python3-scipy python3-gi python3-gi-cairo gir1.2-gtk-3.0 libcodec2-dev libgsm1-dev libusb-1.0-0 libusb-1.0-0-dev libudev-dev python3-setuptools python3-pygccxml python3-thrift libqwt-qt5-6 libqwt-qt5-dev python3-pyqt5.qwt python3-qwt3d-qt5 libspdlog-dev libspdlog1.12 pybind11-dev python3-cppimport python3-pybind11 python3-pybindgen

@@ Line 24: / Line 24: @@
 |style="text-align:center;"| Michael Dickens
 |style="text-align:center;"| Lots of Updates
 |}
 -->
@@ Line 31: / Line 35: @@
 This application note walks through the process to get started with the Data Plane Development Kit (DPDK) driver within UHD.
-==Abstract==
+== Abstract ==
-Up until now, UHD's only support for networked devices was backed by the kernel's sockets implementation. Every call to <code>send()</code> or <code>recv()</code> would cause a context switch and invite the kernel's scheduler to replace our thread with something else. Because the typical scheduler is optimized to distribute CPU time fairly across multiple loads, the timing-critical threads might sporadically be hit with sleeping time, and the thread might be migrated off its current CPU and forced to run on another. The overhead and random latency spikes make it difficult to enable reliable real-time streaming at higher rates.
+UHD's original support for networked devices used the Linux kernel's sockets implementation. Every call to <code>send()</code> or <code>recv()</code> would cause a context switch and invite the kernel's scheduler to replace the UHD thread with something else. Because the typical scheduler is optimized to distribute CPU time fairly across multiple cores, the timing-critical threads might sporadically be hit with sleeping time and the thread might be migrated off its current CPU and forced to run on another. The overhead and random latency spikes caused by these make it difficult to enable reliable real-time streaming at higher rates.
-DPDK is a high-speed packet processing framework that enables a kernel bypass for network drivers. By putting the entire driver in user space, avoiding context switches, and pinning I/O threads to cores, UHD and DPDK combine to largely prevent the latency spikes induced by the scheduler. In addition, the overall overhead for packet processing lowers.
+DPDK is a high-speed packet processing framework that enables kernel bypass for network drivers. By putting the entire driver in user-space, avoiding context switches, and pinning I/O threads to cores, UHD and DPDK combine to largely prevent the latency spikes induced by the Linux thread scheduler. In addition, DPDK lowers the overall overhead for packet processing.
 == Supported Devices ==
@@ Line 41: / Line 47: @@
 === USRPs ===
-DPDK is supported on the following USRP devices, which are those providing 10 GbE (SFP+) and 100 GbE (QSFP28) links:
+DPDK is supported on the following USRP devices, which are those providing 10 GbE (SFP+) and 100 GbE (QSFP28) links, whether physical or virtual:
      E320, N300 / N310, N320 / N321, X300 / X310, X410, X420, X440
@@ Line 119: / Line 125: @@
 == Enable hugepages ==
-DPDK ''requires'' <code>hugepages</code> to be enabled and "large enough". There are multiple ways to enable <code>hugepages</code>. THe following is an easy way to enable this feature and enough allocated for DPDK needs.
+DPDK ''requires'' <code>hugepages</code> to be enabled and "large enough". There are multiple ways to enable <code>hugepages</code>. The following is an easy way to enable this feature and allocate enough <code>hugepages</code> For UHD's DPDK needs.
 Edit your grub configuration file, <code>/etc/default/grub</code> and add the follow parameters to <code>GRUB_CMDLINE_LINUX_DEFAULT</code>:
-     iommu=pt intel_iommu=on hugepages=2048
+     hugepages=2048
-On a vanilla Ubuntu system it should look like this:
+On a vanilla Ubuntu system with Intel CPU, this entry may read like this:
      GRUB_CMDLINE_LINUX_DEFAULT="quiet splash iommu=pt intel_iommu=on hugepages=2048"
@@ Line 142: / Line 148: @@
      ip a
 You must then create a UHD configuration file.
@@ Line 227: / Line 237: @@
 '''Notes:'''
 * Additional information on the [https://files.ettus.com/manual/page_dpdk.html#dpdk_nic_config UHD DPDK configuration file is in the UHD manual].
-* The number of cores listed must be used exactly within the file.
+* The number of cores listed ''should'' be used exactly within the file.
 * The number of NIC link(s) listed must exactly match those specified in the UHD instantiation args.
 * A simple way to move between different DPDK configurations is to create different files and then symlink from the desired file to <code>uhd.conf</code>
 == Additional Host Configuration for NIC Vendors ==
@@ Line 507: / Line 516: @@
 == Known Issues / Troubleshooting ==
-=== Regular Overflows on multi-CPU Systems ===
+=== Regular Data Transport Issues on multi-CPU Systems using NUMA nodes ===
-On Multi-CPU systems each CPU is a NUMA node. The NUMA node contains all of the cores on the CPU. For best performance when using CPU/core isolation ("isocpus" per the section <code> Isolate Cores/CPUs</code> above) make sure that all of the cores are in the same NUMA node.
+On multi-CPU systems, each CPU is a NUMA node. Even on a single CPU system one can intentionally allocate multiple NUMA nodes. A NUMA node contains specific CPU cores along with specific components such NICs and GPUs. For best performance with UHD, use the [https://kb.ettus.com/Getting_Started_with_DPDK_and_UHD#Limit_Execution_CPUs.2FCores <code>taskset</code>] to keep the UHD-based application within a given NUMA node's set of cores and make sure the NUMA node includes all NICs in use by UHD. Adding core isolation is ''not'' required when keeping execution within a specific NUMA node; it may be required for performance reasons.
 === Underruns Every Second with DPDK + Ubuntu ===

@@ Line 1: / Line 1: @@
-==Application Note Number==
+== Application Note Number ==
 '''AN-088'''
 This application note provides various tips and tricks for tuning your host computer for best performance when working with USRP devices.
@@ Line 78: / Line 91: @@
 This applies to Ethernet connected USRPs: N2xx, N3xx, X3xx, E31x, E320, X4xx
-For 1 Gigabit connections, the MTU should be set to <code>1500</code>.
+For 1 GbE links, the MTU should be set to <code>1500</code>.
-For 10 Gigabit connections, the MTU should be set to <code>9000</code>.
+For 10 GbE and 100 GbE links, the MTU should be set to <code>9000</code>.
-It is important to set the value and '''not''' leave it is <code>automatic</code>.
+It is important to ''set'' the value and ''not'' leave it in the default: <code>automatic</code>
 == Increasing Ring Buffers ==
@@ Line 97: / Line 110: @@
 == DPDK ==
-DPDK is supported on N3xx, X3xx and E320 USRPs. DPDK replaces the traditional Linux networking stack with a low overhead user-land based driver. Additional details of using DPDK can be found in the UHD Manual located at the following link: https://files.ettus.com/manual/page_dpdk.html
 == Disable Hyper-threading ==

@@ Line 41: / Line 41: @@
 === USRPs ===
-DPDK is supported on the following USRP devices:
+DPDK is supported on the following USRP devices, which are those providing 10 GbE (SFP+) and 100 GbE (QSFP28) links:
-* E320
+    E320, N300 / N310, N320 / N321, X300 / X310, X410, X420, X440
-* N300 / N310
-* N320 / N321
-* X300 / X310
-* X410
-* X420
-* X440
 === Host Network Cards ===
@@ Line 74: / Line 68: @@
 * DPDK: https://www.dpdk.org/
-** https://doc.dpdk.org/guides-17.11
+* DPDK Docs by Version: https://core.dpdk.org/doc/archives/
-** https://doc.dpdk.org/guides-18.11
+* DPDK Quick Install Guide: https://core.dpdk.org/doc/quick-start/
-** https://doc.dpdk.org/guides-19.11
+* UHD Manual on DPDK: https://files.ettus.com/manual/page_dpdk.html
-** https://doc.dpdk.org/guides-20.11
-** https://doc.dpdk.org/guides-21.11
-** https://doc.dpdk.org/guides-22.11
-** https://doc.dpdk.org/guides-23.11
-** https://doc.dpdk.org/guides-24.11
-** https://doc.dpdk.org/guides-25.11
 * UHD Manual: https://files.ettus.com/manual/page_dpdk.html
-== Dependencies ==
+== UHD DPDK Version Dependencies ==
 * UHD 3.x requires DPDK 17.11
@@ Line 93: / Line 80: @@
 * UHD 4.2 to 4.7 can use any version of DPDK from 18.11 to 21.11
-* UHD 4.8 to 4.9 can use any version of DPDK from 18.11 to 24.11
+* UHD 4.8 and 4.9 can use any version of DPDK from 18.11 to 24.11
 * UHD 4.10 can use any version of DPDK from 19.11 to 25.11
@@ Line 103: / Line 90: @@
      sudo apt install dpdk dpdk-dev
-While it is possible to install DPDK from source, we recommend using the system-provided install unless there is a very good reason to not do so. DPDK can be challenging to ''correctly'' build from source though more recent versions use meson and ninja along with default settings needed by UHD and hence are relatively simple to build and install. If you require installing DPDK from source, the install guide for various versions is noted below:
+While it is possible to install DPDK from source, we recommend using the system-provided install unless there is a very good reason to not do so. DPDK version 18 and older can be challenging to ''correctly'' build from source. DPDK version 19 and newer use meson and ninja along with default settings needed by UHD and hence are relatively simple to build and install. If you require installing DPDK from source, the install guide for various versions is noted below:
 * [https://doc.dpdk.org/guides-17.11/linux_gsg/build_dpdk.html DPDK 17.11]
@@ Line 115: / Line 102: @@
 * [https://doc.dpdk.org/guides-25.11/linux_gsg/build_dpdk.html DPDK 25.11]
-DPDK releases come three times per year in April (version X.04), July (version X.07), and November (version X.11). The X.11 version is more of a formal release. While any ''can'' be used with UHD, we recommend using just the formal releases.
+DPDK releases come three times per year in April (version X.04), July (version X.07), and November (version X.11). The X.11 version is more of a formal  release ("long term service" or LTS). While any ''can'' be used with UHD, we ''strongly'' recommend using just the formal releases.
-NOTE: It is sometimes necessary to use NIC device drivers because of improved feature sets or just getting a NIC to work; the system provided NIC drivers are too old. In this case: (1) remove the system provided DPDK and DPDK-DEV and whatever UHD install is in use; you will need to build these from source. (2) Download and install the new NIC drivers, NVM, and anything else that the NIC needs to be updated to the version needed. (3) Download and install DPDK from source. (4) Download and install UHD from source.
+'''NOTE:''' It is sometimes necessary to manually install NIC device drivers because of improved feature sets or just getting a NIC to work (e.g., the system provided NIC drivers are too old). In this case, to use DPDK one ''must'' build DPDK and UHD from source. Follow these steps in the order noted to guarantee that DPDK is built with the updated NIC drivers and that UHD is built with the noted DPDK:
 == Installing UHD ==

@@ Line 5: / Line 5: @@
 This application note provides various tips and tricks for tuning your host computer for best performance when working with USRP devices.
-==CPU Governor==
+== CPU Governor ==
 Ensure your CPU governor is set to <code>performance</code>. This can be done with the Linux utility <code>cpufrequtils</code>.
@@ Line 52: / Line 55: @@
 ==Adjust Network Buffers==
-This applies to USRP devices connected via Ethernet, such as the N200, N210, N300, N310, N320, N321, X300, X310, E320, X410, X440.
 Note that these settings will not persist across a reboot.
@@ Line 68: / Line 72: @@
      net.core.rmem_default=33554432
-==Adjust Ethernet MTU==
+'''NOTE:''' You may choose to use a larger setting such as 250000000 to guarantee these settings work for ''any'' USRP. Larger numbers require memory allocation but with modern hardware this memory is generally available with plenty of spare.
-This applies to Ethernet connected USRPs (N2xx, N3xx, X3xx, E320).
 For 1 Gigabit connections, the MTU should be set to <code>1500</code>.
@@ Line 75: / Line 82: @@
 For 10 Gigabit connections, the MTU should be set to <code>9000</code>.
-It is important to set the value and '''not''' leave it is <code>automatic</code>
+It is important to set the value and '''not''' leave it is <code>automatic</code>.
-==Increasing Ring Buffers==
+== Increasing Ring Buffers ==
-This applies to Ethernet connected USRPs using a 10 Gb interface (X3xx, N3xx, E320).
-Increasing the Ring Buffers on the NIC may help prevent flow control errors at higher rates.
+This applies to Ethernet connected USRPs using a 10 GbE or 100 GbE interface: N2xx, N3xx, X3xx, E320, X4xx
      sudo ethtool -G <interface> tx 4096 rx 4096
 == DPDK ==
@@ Line 91: / Line 103: @@
 In some applications which require the highest possible CPU performance per core, disabling hyper-threading can provide roughly a 10% increase in core performance, at the cost of having fewer core threads. Hyper-threading is disabled within the BIOS and how to do this varies by motherboard manufacturer. With other techniques listed here, disabling hyper-threading should only be done as a last resort to eek absolute maximum performance from the CPU.
-== Disable KPTI Protections for Spectre/Meltdown==
+== Disable KPTI Protections for Spectre/Meltdown ==
 In some cases, disabling the KPTI protections for the Linux Kernel can increase performance by 10-15%. It is important to note the ramification making this modification can have. This modification is only recommended for systems that absolutely require the best performance and are not connected to the internet.
@@ Line 97: / Line 110: @@
 * https://en.wikipedia.org/wiki/Spectre_(security_vulnerability)
-Disabling KPTI protections can be done by adding the lines below to your <code>/etc/default/grub</code> file at <code>GRUB_CMDLINE_LINUX_DEFAULT=""</code>
+Disabling KPTI protections can be done by adding the lines below to your <code>/etc/default/grub</code> file at <code>GRUB_CMDLINE_LINUX_DEFAULT=""</code>.
      pti=off spectre_v2=off l1tf=off nospec_store_bypass_disable no_stf_barrier
-After modifying the <code>grub</code> file, run the following command to update your configuration and reboot:
+For Linux kernel 6 or higher:
-−
-    sudo update-grub
-−
-−
-−
 [[Category:Application Notes]]

@@ Line 314: / Line 314: @@
 For example, running the <code>benchmark_rate</code> utility after issuing <code>sudo su</code> (one can also run this command simply as <code>sudo /usr/local/lib/uhd/examples/benchmark_rate ....</code>.
-NOTE that the text output from UHD 3 or 4 is about the same; the primary difference will in the initial <code>[INFO]</code> line.
+NOTE that the text output from UHD 3 or 4 is about the same; the primary difference is in the initial <code>[INFO]</code> line.
 <pre>
@@ Line 411: / Line 411: @@
 === Increasing <code>num_recv_frames</code> ===
-If you experience <code>Overflows</code> at higher data rates, adding the device argument <code>num_recv_frames=512</code> can help.
+If you experience <code>Overflows</code> at higher data rates, adding the device argument <code>num_recv_frames=###</code> can help, where <code>###</code> might be <code>500</code> for expected link data throughput of 10-20 Gbps and <code>3000</code> for 80 Gbps. There is no "correct" value, unlike, for example, the number samples-per-packet which is bound by the Ethernet packet size: 1500 Bytes for 1 GbE links and 9000 Bytes ("jumbo packet size") for 10 GbE and 100 GbE links. Higher values require more memory allocation, which for DPDK means higher <code>dpdk_num_mbufs</code> and sometimes <code>dpdk_mbuf_cache_size</code> and  <code>dpdk_num_desc</code>, in the UHD DPDK configuration file.
 === Full Rate Streaming (UHD 3.x only) ===
@@ Line 428: / Line 428: @@
 === Isolate Cores/CPUs ===
-Isolating the cores that are used for DPDK can improve performance. This can be done by adding the <code>isolcpus</code> parameter to your <code>/etc/default/grub</code> file in the <code>GRUB_CMDLINE_LINUX_DEFAULT=""</code> (the "<code>GRUB_CONFIG</code>"). For example, to isolate cores 2 through and including 4, add this entry:
+'''NOTE:''' Isolation cores ''must'' be used along with a [https://kb.ettus.com/Getting_Started_with_DPDK_and_UHD#Limit_Execution_CPUs.2FCores taskset] or other method such that the UHD-based application uses the isolated cores.
      isolcpus=2-4
-NOTE: After saving the <code>GRUB_CONFIG</code> file, execute <code>sudo update-grub</code> and then reboot the computer for the changes to take effect. DPDK handles core isolation during runtime for cores assigned to it, but it is OK to isolate cores used by DPDK via this method. Using just <code>isolcpus</code> does not ''entirely'' isolate cores, nor does it prevent context switching; these are handled by other GRUB parameters and/or system settings.
+'''NOTE:''' After saving the <code>GRUB_CONFIG</code> file, execute <code>sudo update-grub</code> and then reboot the computer for the changes to take effect.
 === Disable System Interrupts on Cores/CPUs ===
-Disabling system interrupts can improve the jitter and performance generally by 1-3%. This can be done by adding the parameters <code>nohz_full</code> and <code>rcu_nocbs</code> to your <code>GRUB_CONFIG</code>. For example, to disable system interrupts on cores 2 through and including 4, add this entry:
+'''NOTE:''' Disabling system interrupts ''should'' be used in conjunction with core isolation, which ''must'' be used along with a [https://kb.ettus.com/Getting_Started_with_DPDK_and_UHD#Limit_Execution_CPUs.2FCores taskset] or other method such that the UHD-based application uses the isolated cores.
-    nohz_full=2-4 rcu_nocbs=2-4
+Disabling system interrupts can improve the jitter and performance. This can be done by adding the parameters <code>nohz_full</code> and <code>rcu_nocbs</code> to your <code>GRUB_CONFIG</code>. For example, to disable the vast majority of system interrupts on cores 2 through and including 4 and their hyperthreaded relations, add this entry:
-NOTE: After saving the <code>GRUB_CONFIG</code> file, execute <code>sudo update-grub</code> and then reboot the computer for the changes to take effect. It is OK to isolate core used by DPDK via this method.
+     nohz_full=2-4,10-12 rcu_nocbs=2-4,10-12 rcu_nocb_poll
 === Streaming on Multiple Channels using 1 Thread Per Stream ===
-If you're streaming on multiple channels simultaneously, you can create multiple streamer objects on separate threads. This can be accomplished with the <code>benchmark_rate</code> example by using the parameter <code>--multi_streamer</code>.
+If you're streaming on multiple channels simultaneously, you can create multiple streamer objects on separate threads. For example, this can be accomplished with the <code>benchmark_rate</code> example by using the parameter <code>--multi_streamer</code> -- which assigns 1 channel per thread, whether TX or RX.
 === Elevated Streaming Thread Priority ===
@@ Line 462: / Line 486: @@
      taskset -c "2-4"
-NOTE: For best performance do ''not'' include the cores used by DPDK in the <code>dpdk_corelist</code> argument in the <code>taskset</code>.
+'''NOTE:''' For best performance do ''not'' include the cores used by DPDK in the <code>dpdk_corelist</code> argument in the <code>taskset</code> nor the hyperthreaded cores. The "DPDK control" core ''may'' be included in the taskset because it is not dedicated by DPDK for its sole use.
 === Stopping Extraneous Processes ===
@@ Line 477: / Line 501: @@
      systemctl stop gdm
 === Disable Hyper-threading ===