need help: scheduling

need help: scheduling

[Gunter]

Hello

I need help about scheduling. I hope i understand the basics for my
question: An active prozess counts the remaining cpu time in jifies. By
every timer interrupt the scheduler decrements the variable time_slice.

Where is the scheduler initializing the interrupt timer (init_timer).
And where gets the struct timer_list the next interrupt (expires). At
last i want know where the scheduler calls add_timer. Or is there an
other way?

Thank You
Gunter

Re: need help: scheduling

[Steven Rostedt]

On Mon, 2005-04-18 at 15:00 +0200, Gunter wrote:
> Hello
> 
> I need help about scheduling. I hope i understand the basics for my
> question: An active prozess counts the remaining cpu time in jifies. By
> every timer interrupt the scheduler decrements the variable time_slice.
> 

Yes, this is correct.

> Where is the scheduler initializing the interrupt timer (init_timer).
> And where gets the struct timer_list the next interrupt (expires). At
> last i want know where the scheduler calls add_timer. Or is there an
> other way?
> 

The timer_list you are mentioning is used for events that need to go off
at a certain jiffy. This is not what the scheduler uses.  The
schedule_tick (which keeps track of the time_slices of processes) goes
off at a timer interrupt once a jiffy. This is architecture dependent,
and for x86 you can take a look at arch/i386/kernel/time.c
timer_interrupt.  This is (usually) setup in
arch/i386/mach-default/setup.c. Search for timer_interrupt for the
details, and then follow the trail there.

-- Steve