scheduler rewrite

Antonio Vargas windenntw at
Tue Dec 7 09:39:21 PST 2004

On Fri, 3 Dec 2004 10:47:45 -0800 (PST), Matthew Dillon
<dillon at 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 at 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 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.

More information about the Kernel mailing list