Using ionice (with examples)

ionice is a command-line tool that allows users to get or set the I/O scheduling class and priority of a program. This can be useful in managing system resources and ensuring that certain processes are given priority for I/O operations.

In this article, we will explore eight different use cases of ionice, including setting I/O scheduling class of a running process, running a command with custom I/O scheduling class and priority, and printing the I/O scheduling class and priority of a running process.

Set I/O scheduling class of a running process

To set the I/O scheduling class of a running process, we can use the following command:

ionice -c scheduling_class -p pid

• scheduling_class refers to the desired scheduling class for the process. The three available classes are:

  • 1 (real-time): Provides the highest priority for I/O operations.
  • 2 (best-effort): Default class for most processes.
  • 3 (idle): Lowest priority for I/O operations.

• pid is the Process IDentifier of the running process.

Motivation: Changing the I/O scheduling class of a running process can help optimize the use of system resources and prioritize critical tasks.

Example:

ionice -c 2 -p 1234

This command sets the I/O scheduling class of the process with PID 1234 to “best-effort”.

Run a command with custom I/O scheduling class and priority

To run a command with a custom I/O scheduling class and priority, we can use the following command:

ionice -c scheduling_class -n priority command

• scheduling_class refers to the desired scheduling class for the command.
• priority specifies the priority level for the command. Priority levels range from 0 (highest) to 7 (lowest).
• command is the command to be executed with the specified I/O scheduling class and priority.

Motivation: Running a specific command with a custom I/O scheduling class and priority can ensure that it receives the necessary resources for efficient I/O operations.

Example:

ionice -c 3 -n 4 ls -l

This command runs the “ls -l” command with I/O scheduling class “idle” and priority level 4.

Print the I/O scheduling class and priority of a running process

To print the I/O scheduling class and priority of a running process, we can use the following command:

ionice -p pid

• pid is the Process IDentifier of the running process.

Motivation: Checking the I/O scheduling class and priority of a process can help in understanding its resource allocation and current system impact.

Example:

ionice -p 5678

This command prints the I/O scheduling class and priority of the process with PID 5678.

By using these different variations of the ionice command, users can effectively manage and optimize I/O operations on their system. Whether it’s adjusting the I/O scheduling class of a running process, running a command with custom scheduling and priority, or simply printing the I/O information of a process, ionice provides a flexible and powerful tool for managing I/O resources.