How to use the command chrt (with examples)

The chrt command is used to manipulate the real-time attributes of a process in Linux. It allows users to view and modify the scheduling policy and priority of a process or a group of processes.

Use case 1: Display attributes of a process

Code:

chrt --pid <PID>

Motivation: This use case is helpful when you want to view the real-time attributes of a specific process. It provides information about the scheduling policy and priority of the process.

Explanation: The --pid option is used to specify the process ID (PID) for which you want to display the attributes.

Example output:

pid 12345's current scheduling policy: SCHED_OTHER
pid 12345's current scheduling priority: 0

Use case 2: Display attributes of all threads of a process

Code:

chrt --all-tasks --pid <PID>

Motivation: When dealing with multi-threaded processes, it is often useful to view the real-time attributes of all the threads belonging to a specific process. This use case allows you to retrieve information about the scheduling policies and priorities of all the threads.

Explanation: The --all-tasks option is used to display attributes of all threads instead of just the main process. The --pid option is used to specify the process ID (PID) for which you want to display the attributes.

Example output:

tid 12345's current scheduling policy: SCHED_FIFO
tid 12345's current scheduling priority: 2

Use case 3: Display the min/max priority values that can be used with chrt

Code:

chrt --max

Motivation: It is important to know the range of priority values that can be used with the chrt command. This use case provides information about the minimum and maximum priority values that can be set.

Explanation: The --max option is used to display the minimum and maximum priority values that are supported by the system.

Example output:

min priority: -20
max priority: 19

Use case 4: Set the scheduling policy for a process

Code:

chrt --pid <PID> --deadline|idle|batch|rr|fifo|other

Motivation: Sometimes, it is necessary to modify the scheduling policy of a process to meet specific real-time requirements. This use case allows you to set the scheduling policy to one of the available options: deadline, idle, batch, rr (round-robin), fifo (first-in-first-out), or other.

Explanation: The --pid option is used to specify the process ID (PID) for which you want to set the scheduling policy. The --deadline, --idle, --batch, --rr, --fifo, or --other option is used to set the corresponding scheduling policy.

Example output:

Scheduling policy of process with PID 12345 set to 'rr'

Conclusion:

The chrt command provides a set of useful features for manipulating the real-time attributes of processes in Linux. It allows you to view the attributes of a process or a group of processes, display the range of priority values, and modify the scheduling policy. By understanding and utilizing these features effectively, you can optimize the execution of real-time applications and ensure their reliable performance.