DragonFly kernel List (threaded) for 2004-12
Re: scheduler rewrite
On Fri, 3 Dec 2004 10:47:45 -0800 (PST), Matthew Dillon
> :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.
> :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).
> Matthew Dillon
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.