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SubjectRe: Scheduler Cleanup

On Mon, 26 Nov 2001, Mike Kravetz wrote:

> I'm happy to see the cleanup of scheduler code that went into
> 2.4.15/16. One small difference in behavior (I think) is that the
> currently running task is not given preference over other tasks on the
> runqueue with the same 'goodness' value. I would think giving the
> current task preference is a good thing (especially in light of recent
> discussions about too frequent moving/rescheduling of tasks). Can
> someone provide the rational for this change? Was it just the result
> of making the code cleaner? Is it believed that this won't really
> make a difference?

i've done this change as part of the sched_yield() fixes/cleanups, and the
main reason for it is that the current process is preferred *anyway*, due
to getting the +1 boost via current->mm == this_mm in goodness().

(and besides, the percentage/probability of cases where we'd fail reselect
a runnable process where the previous scheduler would reselect it is very
very low. It does not justify adding a branch to the scheduler hotpath
IMO. In 99.9% of the cases if a runnable process is executing schedule()
then there is a higher priority process around that will win the next
selection. Or if there is a wakeup race, then the process will win the
selection very likely because it won the previous selection.)

Ingo

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