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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 the QNX OS 8.0.
OS Components & Operations
Performance Tuning User's Guide
Networking stack (io-sock)
Scaling the network interface driver framework (iflib)

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX 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 the QNX OS 8.0.
- Quickstart Guide
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  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
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    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.
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    The Building Embedded Systems guide is intended for developers who are developing or building BSPs for QNX OS embedded systems.
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    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.
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  - High-Performance Networking Stack (io-sock) User's Guide
    This guide contains instructions for implementing and using the QNX OS High-Performance Networking Stack and its manager, io-sock.
  - PCI Server User's Guide
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    The QNX OS User's Guide is intended for all users of a QNX OS system, from system administrators to end users.
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  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX OS system and developers who want to create a QNX OS resource manager free from vulnerabilities.
- Utilities & Libraries
- Migrating to QNX OS 8.0
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX OS in the Amazon cloud environment.
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX^® Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX^® Operating System (OS) applications and systems.
QNX Hypervisor User's Guide
This User's Guide explains the QNX hypervisor architecture and provides instructions for installing and running a QNX Hypervisor system, changing system components and configuration, and using hypervisor features such as virtual devices (vdevs).
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

Scaling the network interface driver framework (iflib)

QNX SDP8.0Performance Tuning User GuideUser

You may scale iflib for larger systems with the following method:

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 -m phy -m pci -d ix

Page updated: March 05, 2025