Re: 2.6.15-rc5-mm2 :-)

[Con Kolivas <kernel@kolivas.org>]

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On Tuesday 13 December 2005 22:13, Maciej Soltysiak wrote:
> Hello Con,
>
> Tuesday, December 13, 2005, 6:52:09 AM, you wrote:
> > I missed this announcement (been on leave for a while). This SCHED_BATCH
> > implementation is by Ingo and it it is not "idle" scheduling as I have
> > implemented in the staircase scheduler. This is just to restrict a task
> > to not having any interactive bonus at any stage and to have predictable
> > scheduling behaviour I guess.
>
> Thanks a lot. That's good anyway.
>
> If I understand correctly, if Ingo's version gets merged with linus' tree
> your implementions of SCHED_BATCH in -ck will be replacing the one from
> Ingo.

Yes. SCHED_BATCH in Ingo's implementation is more like turning off the 
interactive setting in staircase, and the idle scheduling staircase offers is 
extremely useful.

> A silly question. Is SCHED_BATCH-kind-of-thing a standard in Unices or
> general operating system engineering know-how? Or is this concept only
> available for Linux?

Fairly standard in Unices but prone to all sorts of priority inversion 
starvation scenarios so very few implement it. In freebsd for example you can 
use their idle scheduling only if you are root to prevent this starvation - 
which kind of makes it useless in practice. My implementation is fairly 
robust at avoiding the priority inversion problem - at least I haven't seen a 
bug report about it for years since I address it :)

Cheers,
Con

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