This topic describes how to use the irqbalance-ng feature provided by the platform to automatically configure CPU affinity for the interrupt requests (IRQs) of physical network interfaces, thereby improving network performance.

Applicable scenario

In high network traffic scenarios, a large number of network interface IRQs may concentrate on a single CPU, causing delays in packet transmission and reception. irqbalance-ng operates in a periodic scanning mode, automatically checking and configuring the CPU affinity (via /proc/irq/{irq_id}/smp_affinity) of physical network interfaces. This prevents uneven CPU load when network interface IRQs are processed, thereby improving network performance.

In scenarios where multiple Network Namespaces are configured, irqbalance-ng can automatically identify network interface information for each namespace and configure CPU affinity for the network interface IRQs.

Usage notes

The tool can only be installed and used in the images described in the following table.

Image type	Operating system version
veLinux	veLinux 1.0 64 bit veLinux 2.0 64 bit
CentOS	CentOS 7.x 64 bit CentOS 8.3 64 bit CentOS Stream 9.x 64 bit
Ubuntu	Ubuntu 18.04 64 bit Ubuntu 20.04 64 bit Ubuntu 22.04 64 bit Ubuntu 14.04 64 bit
Debian	64-bit Debian 10 Debian 12 64 bit
Red Hat Enterprise Linux (RHEL)	RHEL 7.8 64 bit RHEL 8.8 64 bit RHEL 9.2 64 bit RHEL 9.3 64 bit
AlmaLinux	AlmaLinux 8.x 64 bit AlmaLinux 9.x 64 bit

Concepts

Concept	Description
IRQ	An interrupt request (IRQ) refers to an electrical signal actively sent by a device to the CPU, causing the CPU to stop its current task and process the received interrupt request.
irqbalance	A daemon used to help balance the CPU load generated by interrupts across all system CPUs.
CPU affinity	CPU affinity, also known as CPU binding, refers to the tendency of processes or IRQs to run on a specified CPU for an extended period without being migrated to other processors.
NUMA	Non-Uniform Memory Access (NUMA) is a memory architecture designed for multiprocessor computers. The memory access speed depends on the location of memory relative to the processor.
Network Namespace	A method provided by Linux for isolating system-wide resources. The method works by placing global resources of the system into different namespaces to achieve isolation. Programs in different namespaces can have their own independent set of system resources.

Procedure

Install irqbalance-ng

You can log in to the target Linux instance and install the irqbalance-ng tool for the corresponding operating system.

veLinux

CentOS

Debian

Ubuntu

Red Hat/AlmaLinux

Execute the following command to configure the extra-tools software repository for the image.

veLinux 1.0
veLinux 2.0

echo 'deb http://mirrors.ivolces.com/extra-tools/velinux/ orion main' >> /etc/apt/sources.list.d/extra-tools.list
wget -O - http://mirrors.ivolces.com/extra-tools/velinux/GPG-KEY-system | apt-key add -

Execute the following command to update the software repository information.

apt-get update

Execute the following command to install irqbalance-ng.

apt-get install irqbalance-ng

Manage irqbalance-ng

View the running status

Log in to the target Linux instance.

Execute the following command to check whether irqbalance-ng is running as expected.

systemctl status irqbalance-ng.service

Configure rules for running the tool

You can modify the configuration file of irqbalance-ng to adjust settings such as the interval at which irqbalance-ng checks or adjusts CPU affinity for network interface IRQs, and the list of CPUs that handle network interface IRQs.

Log in to the target Linux instance.

Execute the following command to edit the configuration file.

vim /etc/default/irqbalance-ng

Press the i key to enter edit mode, and modify the irqbalance-ng configuration based on your needs.

Parameter description

Parameter	Description	Sample value
debug	The level of logs printed by the irqbalance-ng service. Valid values: 0: Logs of the error level are printed. 1: Logs of the info and error levels are printed. This is the default value. 2: Logs of the debug, info, and error levels are printed. tip The storage path for irqbalance-ng logs is /var/log/irqbalance-ng.log.	1
distinguish	The default setting. Do not modify the setting.	1
peroid	The interval (in seconds) at which irqbalance-ng checks or adjusts CPU affinity for network interface IRQs. The default value is 60.	60
cpu_lists	The CPUs specified to handle network interface IRQs. The default value is "", which specifies all CPUs. You can pass in multiple CPU IDs, and use commas (,) to separate them. You can use - to pass in a range of consecutive CPU IDs. tip You can execute the lscpu, numactl --hardware, or lshw command to view the CPU IDs. In the following figure, the lscpu command is used as an example. 0-7 indicates that the IDs of the CPUs are 0, 1, 2, 3, 4, 5, 6, and 7.	"1,4,5,10-15,20"
lib_path	The path to library files when you use the installation package to install the tool. We recommend that you do not modify the path.	-
net_path	The path to files related to network interfaces in the image. We recommend that you do not modify the path.	-
cpu_path	The path to the CPU device file in the image. We recommend that you do not modify the path.	-
numa_path	The path to the NUMA file in the image. We recommend that you do not modify the path.	-

Press Esc, enter :wq, and then press Enter to save the modifications and close the file.

After you modify the file, execute the following command to restart irqbalance-ng for the modifications to take effect.

systemctl restart irqbalance-ng

You can execute the following command to view the binding information between IRQs and CPUs.

for i in `cat /proc/interrupts | grep -E "input|output" | awk -F ' ' '{print $1}' | awk -F ':' '{print $1}'` ;do echo "irq_"$i ":" `cat /proc/irq/$i/smp_affinity_list` ;done

Stop irqbalance-ng

You can execute the following command to stop periodic CPU affinity configuration for IRQs performed by irqbalance-ng.

systemctl stop irqbalance-ng.service

You can also execute the following command to disable irqbalance-ng from starting automatically when the instance starts.

systemctl disable irqbalance-ng.service

Uninstall irqbalance-ng

CentOS/AlmaLinux/RHEL

yum remove irqbalance-ng

Debian/Ubuntu

apt-get remove --purge irqbalance-ng

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