Linux Priority Levels

Linux Priority Levels

[Ajay Jain]

Hi,

I need a deeper understanding of priorities of linux processes and
threads, especially on Linux PPC. I have done some good reading, but
found no material to be complete and therefore I am raising a few
questions below.

1) In Linux processes have a static priority level 0, with nice values
-20 to +19. Then it has RT priority levels 1 - 99. My question is, do
the nice values apply to all processes or do they apply only to
priority 0?

2) How many total priority levels does the kernel have? On one hand,
-20 is the highest priority, on the other hand +99 is the highest. How
do these values converge?

Please help me to answer these and depending on the reply I would
shoot more questions. In case you have a comprehensive reading
material to refer, please advise.

Thanks,
Ajay.

Re: Linux Priority Levels

[Michael Neuling]

> I need a deeper understanding of priorities of linux processes and
> threads, especially on Linux PPC. I have done some good reading, but
> found no material to be complete and therefore I am raising a few
> questions below.
> 
> 1) In Linux processes have a static priority level 0, with nice values
> -20 to +19. Then it has RT priority levels 1 - 99. My question is, do
> the nice values apply to all processes or do they apply only to
> priority 0?
> 
> 2) How many total priority levels does the kernel have? On one hand,
> -20 is the highest priority, on the other hand +99 is the highest. How
> do these values converge?
> 
> Please help me to answer these and depending on the reply I would
> shoot more questions. In case you have a comprehensive reading
> material to refer, please advise.

man sched_setscheduler has a good description of these levels and how RT
and non RT processes interact.

Mikey