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QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running QNX Neutrino 7.1.
OS Components & Operations
High-Performance Networking Stack (io-sock) User's Guide
This guide contains instructions for implementing and using the QNX Neutrino High-Performance Networking Stack and its manager, io-sock.
Tuning the io-sock networking stack
Scaling the network interface driver framework (iflib)

QNX Momentics IDE User's Guide
This User's Guide describes version 7.1 of the Integrated Development Environment (IDE) that's part of the QNX Momentics tool suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running QNX Neutrino 7.1.
- Quickstart Guide
- OS Components & Operations
  - Adaptive Partitioning User's Guide
  - Boot Optimization Guide
    The Boot Optimization Guide describes techniques you can use to reduce the time from your board's initial power on until you have a fully functional QNX system running on the board.
  - Building Embedded Systems
    The Building Embedded Systems guide is intended for developers who are developing or building BSPs for QNX Neutrino RTOS embedded systems.
  - Core Networking Stack User's Guide
    This guide introduces you to the QNX Neutrino Core Networking stack and its manager, io-pkt.
  - Customizing a BSP
    While QNX provides Board Support Packages (BSPs) for many common platforms and their individual variants, in some cases, you need a BSP for a board that QNX does not provide. If this is the case, you can modify a QNX BSP or develop your own.
  - Device Publishers Developer's Guide
  - High Availability Framework Developer's Guide
  - High-Performance Networking Stack (io-sock) User's Guide
    This guide contains instructions for implementing and using the QNX Neutrino High-Performance Networking Stack and its manager, io-sock.
    - Overview
    - Privilege Control
      Like other components that run on QNX Neutrino, the privileged operations required by io-sock and networking components are protected by process manager abilities. These abilities are configured either directly by the components themselves, or, preferably, via security policies that are defined by the system integrator.
    - Packet Filtering
    - Starting io-sock and Driver Management
    - Running io-sock with diagnostic features
    - Tuning the io-sock networking stack
    - Migrating an Application to the io-sock Networking Stack and Manager
      Applications that use io-pkt can be modified to use io-sock. QNX recommends the following initial modifications to make them compatible.
    - Modifying a BSP to Support io-sock
      If QNX does not provide a BSP that supports io-sock for your target hardware, you need to create one. To simplify the process, QNX recommends that you start with the io-sock-compatible BSP provided by QNX that most closely matches your target's specifications.
    - Socket API
      The io-sock networking stack provides socket functions ported from FreeBSD as well as io-sock-specific ones.
    - Utilities and Driver Reference
      The io-sock networking stack and manager uses new and updated QNX Neutrino utilities, services, and drivers.
    - Writing Network Drivers for io-sock
    - A Hardware-Independent Sample Driver
    - Adding PTP into io-sock Network Drivers
      This appendix describes how to add 2-Step Precision Time Protocol (PTP) Ethernet packet timestamping functionality into an io-sock driver.
    - devs-qwdi_dhd_pcie-version.so
      Driver for Cypress DHD PCIE-based WLAN devices
  - Instant Device Activation
  - Migrating to QNX SDP 7.1
  - PCI Server User's Guide
  - Persistent Publish/Subscribe Developer's Guide
  - Platform-independent Publish/Subscribe Developer's Guide
    This guide is intended for application developers who want to use the Platform-independent Publish Subscribe (PiPS) framework to exchange information with other applications. First, the overall PiPS design and data-exchange model are explained. Then, tutorials on using PiPS are given. These tutorials cover key tasks such as selecting a publish-subscribe provider to use and writing plugins that read and write custom data types.
  - QDB Developer's Guide
  - QNX Helpers Developer's Guide
    These libraries provide QNX helpers, including helpers that assist with logging, string conversion, and number and type sizes.
  - SMMUMAN User's Guide
  - System Analysis Toolkit (SAT) User's Guide
  - System Architecture
    The System Architecture guide accompanies the QNX Neutrino RTOS and is intended for both application developers and end-users.
  - Technotes
  - User's Guide
    The QNX Neutrino User's Guide is intended for all users of a QNX Neutrino RTOS system, from system administrators to end users.
- Audio & Graphics API
- Multimedia
- Networking Middleware
- Programming
- Sensor Framework
- System Security Guide
  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX Neutrino RTOS system and developers who want to create a QNX Neutrino resource manager free from vulnerabilities.
- Utilities & Libraries
QNX Hypervisor
The QNX Hypervisor allows you to run multiple OSs on a target system so you can separate critical and non-critical functions, support a wide variety of applications, and reduce hardware costs.
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX software in Amazon Web Services (AWS) and Microsoft Azure (Azure).
QNX Advanced Virtualization Frameworks User's Guide
This User's Guide is aimed at all systems integrators and developers who want to design and build embedded systems using the QNX Advanced Virtualization Frameworks.
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation and explains how to obtain technical support.

Scaling the network interface driver framework (iflib)

You can scale iflib for larger systems by setting the number of PCI interrupts and queues.

Setting the number of PCI interrupts and queues

By default, the iflib framework used by many PCI drivers allocates a PCI MSI-X interrupt and queue for each CPU core to implement receive-side scaling (RSS) on each interface. In a system with many such interfaces, this mechanism can result in large numbers of interrupts allocated and multiple queues running on each core.

Because there are a limited number of MSI-X interrupts available in a system, high core and interface counts can lead to the system running out of interrupts. These errors are reported in slog2info. For example:

Jan 10 23:55:14.235 io_sock.184334 main_buffer 131 ixl2: Failed to enable MSI-X on 3:0:2 :The Requested Number And Type Of Interrupts Are Unavailable Or Could Not Be Reserved With Current Request Type [(PCI_ERR_IRQ_NOT_AVAIL)]

In addition, each queue is implemented as a thread, and multiple queues running on each core can lead to poor performance with excessive context switching between the threads.

You can resolve both these issues by using a sysctl tunable to set the number of queues per interface to an appropriate value rather than letting iflib use the default (the number of CPUs). The tunable uses the format: dev.device_type.device_instance.iflib.override_nrxqs.

For example, in a system with 24 CPUs and eight interfaces, the default total number of interrupts and queue processing threads is 192. To reduce it to 24, first create the configuration file /etc/io-sock.conf with the following contents:

dev.ix.0.iflib.override_nrxqs="3"
dev.ix.1.iflib.override_nrxqs="3"
dev.ix.2.iflib.override_nrxqs="3"
dev.ix.3.iflib.override_nrxqs="3"
dev.ix.4.iflib.override_nrxqs="3"
dev.ix.5.iflib.override_nrxqs="3"
dev.ix.6.iflib.override_nrxqs="3"
dev.ix.7.iflib.override_nrxqs="3"
dev.ix.0.iflib.override_ntxqs="3"
dev.ix.1.iflib.override_ntxqs="3"
dev.ix.2.iflib.override_ntxqs="3"
dev.ix.3.iflib.override_ntxqs="3"
dev.ix.4.iflib.override_ntxqs="3"
dev.ix.5.iflib.override_ntxqs="3"
dev.ix.6.iflib.override_ntxqs="3"
dev.ix.7.iflib.override_ntxqs="3"

Then, pass the file to io-sock when you start it. For example:

io-sock -o config=/etc/iosock.conf -d ixl

Page updated: March 12, 2026