Hi,

I want to set my program with highest priority for real-time processes. I understand the priority for real-time processes ranges from 1-99, but I get completely confused after reading Understanding the Linux Kernel and the manual of sched_get_priority_max(): which value has higher priority? either 1 or 99. Understanding the Linux Kernel says 1 has highest priority but sched_get_priority_max() returns 99 for SCHED_FIFO and SCHED_RR policy.

Could anyone please tell me which one is right?

Thank you,
Zheng Da

You will never get "real" real-time, with determinism and all things included in its definition using normal linux kernel.

use the nice command. this can alter a commands priority. Look through the documentation because using this command incorrectly and bring your system to a crawl as all processing power could potentially be used on this one process.

edit: oops just reread your post. Sorry that probably won't help you.


I believe that closer to a negative value yeilds a higher priority.

I don't really need "real" real-time. What I want is to run my program with the highest priority thus it can occupy the whole CPU time. Using nice() cannot make a program with real-time priority though it can get higher priority.

If my system doesn't contain any processes with real-time priority, it's probably ok to use any real-time priority. But what surprises me is that when I run my program with the priority 99 and run a compiler, my program is noticeably slower. Note: I measure the elapsed time after the process uses real-time priority. I think there wasn't any error when changing the priority.

So can using the priority 99 fulfill my requirement (see above)?

Thank you,
Zheng Da