Re: Ada Task Priorities (Windows vs Linux)

[Robert A Duff <bobduff@shell01.TheWorld.com>]

"AAFellow@hotmail.com" <AAFellow@hotmail.com> writes:

> Hi Everyone,
> 
> How are tasks prioritized in Ada when running on Linux (compared to
> Windows).  I wrote a small test program that I ran in Windows, and it
> seems that the higher the number that I set the task's priority to, the
> higher the priority that is given to that task (I thought the opposite
> was true?)

In Ada, higher numbers mean higher priority.

> In Linux (using GNAT complier), how are the priorities mapped?  I know
> a lower number means a higher priority, with a range of -20 to 19 and a
> default of 0.  Do we just use these same numbers in the Ada code when
> setting the priorities of the tasks?

No.  You use the numbers in the range System.Priority
(or sometimes, System.Interrupt_Priority).
The default is System.Default_Priority.

Look at the source code for package System to see what the numbers are.

The Ada run-time system will map these numbers to whatever the operating
system uses.  If the operating system thinks lower numbers mean higher
priority, then the Ada run-time system will take that into account.

> Also, (so we can verify we have set the priorities correctly) does
> Linux provide a way to actually see what priority the OS has given to
> tasks that the Ada code has started?  Are there any tools availible
> that can do this? 

I think the 'top' program will show such info.  Not sure.

- Bob