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DragonFly kernel List (threaded) for 2004-12
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Re: scheduler rewrite

From: Antonio Vargas <windenntw@xxxxxxxxx>
Date: Tue, 7 Dec 2004 18:34:58 +0100

On Fri, 3 Dec 2004 10:47:45 -0800 (PST), Matthew Dillon
<dillon@xxxxxxxxxxxxxxxxxxxx> wrote:
> :
> :That basically sounds like ULE to me. Do you plan to
> :adapt ULE, make something separate but similar, or
> :make something separate and radically different? (I
> :suppose their might be some other in-between options
> :too.) I was actually somewhat surprised by FreeBSD5's
> :abandonment of ULE. I had been using it without any
> :significant problems. Of course, if I was playing
> :music, it sounded bad when I unpacked big port
> :tarballs, but that happens with the old scheduler too.
> :Anyway, I'm just looking for more info about what
> :you're thinking about for the scheduler.
> :
> :Thanks,
> :
> :=====
> :--
> :Evan Dower
>     No, we won't be adopting ULE.  I've written a dozen schedulers
>     over the last 20 years, I can do a much better job IMHO then ULE.
>     There have been discussions about the scheduler on this list in
>     the past.  Basically it is a two-stage job.  The first stage would
>     be to create an API to allow different userland schedulers to be
>     loaded on-the-fly (on a live system), and possibly even allow multiple
>     schedulers to operate in parallel.  This is possible because everything
>     winds up being scheduled by LWKT at the lowest level anyway.  That is,
>     the userland scheduler is only determining when user processes run and
>     on what cpu they run and is not actually responsible for the mechanics
>     of running the processes.
>     The second stage would be to then write a new scheduler using the API.
>     LWKT itself uses a strict fixed priority model and round-robins tasks
>     running at the same priority.  This is the best model to use for
>     kernel threads (interrupts, software interrupts, protocol threads,
>     etc.  'user' threads usually have the lowest priority).
>                                         -Matt
>                                         Matthew Dillon
>                                         <dillon@xxxxxxxxxxxxx>

Matt, if I recall correctly, on Amiga we had a shareware program which
manipulated he usually static priorities for each task according to
fairness rules, it was called executive... are you advocating
mantaining the same split-up, kernel with fixed prios and then
userland scheduler adjusting these "fixed" prios?

ps. goto http://de.aminet.net/aminetbin/find?executive and then executive.lha

Greetz, Antonio Vargas aka winden of network


Las cosas no son lo que parecen, excepto cuando parecen lo que si son.

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