Re: question re: scheduling policies

David A Rusling (rusling@linux.reo.dec.com)
Thu, 17 Jul 1997 15:48:20 +0100

Adam Mckee wrote:
>
> Hello all. I am new to the wacky world of kernel hacking, so this
> question may be silly, but...
>
> In kernel/sched.c:goodness(), I am puzzled by the following:
>
> /*
> * Realtime process, select the first one on the
> * runqueue (taking priorities within processes
> * into account).
> */
> if (p->policy != SCHED_OTHER)
> return 1000 + p->rt_priority;
>
> I thought SCHED_OTHER *was* real-time... this snippet implies that
> SCHED_RR and SCHED_FIFO are real-time. Is this true?
>

SCHED_RR is Round Robin and SCHED_FIFO is First In, First Out: both
are real time scheduling policies. The give away is that the 'rt_'
fields are only used by the "real time" processes. Basically they
add weight so that they get selected before other, non-real time,
processes by the scheduler.

> Thanks for your help!
>
> -- Adam

-- 
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David A Rusling				Principal Engineer
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