Ubuntu Pro Real Time 应用实时性相关技术咨询

Hey JoelP! Let's walk through your questions about Ubuntu Pro's Realtime kernel support clearly and practically:

1. Does Realtime automatically apply to the first launched application? #

Nope, it doesn't. Ubuntu Pro's Realtime kernel provides the system-level capability to support real-time scheduling, but it won't automatically assign real-time priorities to any application—even the first one you launch. You need to explicitly configure or launch your target application with real-time scheduling policies.

2. How to check if an application is using real-time scheduling? #

You can use these straightforward commands to verify:

• Using ps: Run ps -o pid,comm,cls -p <YOUR_APP_PID> (replace <YOUR_APP_PID> with your application's process ID). Look at the cls column—if it shows RR (Round Robin) or FIFO, your app is using a real-time scheduling policy.
• Using chrt: Execute chrt -p <YOUR_APP_PID>. The output will display the current scheduling policy; lines like current scheduling policy: SCHED_FIFO or current scheduling policy: SCHED_RR confirm real-time is active for that process.

3. Does Ubuntu Pro handle real-time application setup in the background? #

Ubuntu Pro’s role here is to deliver the optimized Realtime kernel, pre-tuned system settings to support real-time workloads, and official support—it doesn’t automatically configure your applications to use real-time scheduling. You’ll need to set this up manually for your target app.

Quick guide to run your app with real-time support #

To test your application with real-time scheduling for your comparison:

• Launch it directly with a real-time policy using chrt:

  chrt -f 99 ./your-application-executable
  

  Here, -f specifies the SCHED_FIFO policy (you can use -r for SCHED_RR instead), and 99 is the highest possible real-time priority (ranges from 1 to 99—higher values mean higher priority).
• If you don’t want to use sudo every time, grant your user permission to set real-time priorities by editing /etc/security/limits.conf and adding these lines:

  your-username soft rtprio 99
  your-username hard rtprio 99
  

  Log out and back in for this change to take effect.

For your comparison test: first run the app on standard Ubuntu 24.04.1 (no real-time tweaks), record metrics like latency or response times that matter for your use case. Then repeat on Ubuntu Pro’s Realtime kernel with the app launched via chrt—you should see noticeable improvements in consistent low latency if your workload benefits from real-time scheduling.

备注：内容来源于stack exchange，提问作者JoelP