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    SubjectRe: [ANNOUNCE] RSDL completely fair starvation free interactive cpu scheduler
    On Tue, 2007-03-06 at 05:41 +0100, Willy Tarreau wrote:
    > On Tue, Mar 06, 2007 at 11:18:44AM +1100, Con Kolivas wrote:
    > > On Tuesday 06 March 2007 10:05, Bill Davidsen wrote:
    > > > jos poortvliet wrote:
    > > > > Well, imho his current staircase scheduler already does a better job
    > > > > compared to mainline, but it won't make it in (or at least, it's not
    > > > > likely). So we can hope this WILL make it into mainline, but I wouldn't
    > > > > count on it.
    > > >
    > > > Wrong problem, what is really needed is to get CPU scheduler choice into
    > > > mainline, just as i/o scheduler finally did. Con has noted that for some
    > > > loads this will present suboptimal performance, as will his -ck patches,
    > > > as will the default scheduler. Instead of trying to make ANY one size
    > > > fit all, we should have a means to select, at runtime, between any of
    > > > the schedulers, and preferably to define an interface by which a user
    > > > can insert a new scheduler in the kernel (compile in, I don't mean
    > > > plugable) with clear and well defined rules for how that can be done.
    > >
    > > Been there, done that. Wli wrote the infrastructure for plugsched; I took his
    > > code and got it booting and ported 3 or so different scheduler designs. It
    > > allowed you to build as few or as many different schedulers into the kernel
    > > and either boot the only one you built into your kernel, or choose a
    > > scheduler at boot time. That code got permavetoed by both Ingo and Linus.
    > > After that I gave up on that code and handed it over to Peter Williams who
    > > still maintains it. So please note that I pushed the plugsched barrow
    > > previously and still don't think it's a bad idea, but the maintainers think
    > > it's the wrong approach.
    > In a way, I think they are right. Let me explain. Pluggable schedulers are
    > useful when you want to switch away from the default one. This is very useful
    > during development of a new scheduler, as well as when you're not satisfied
    > with the default scheduler. Having this feature will incitate many people to
    > develop their own scheduler for their very specific workload, and nothing
    > generic. It's a bit what happened after all : you, Peter, Nick, and Mike
    > have worked a lot trying to provide alternative solutions.
    > But when you think about it, there are other OSes which have only one scheduler
    > and which behave very well with tens of thousands of tasks and scale very well
    > with lots of CPUs (eg: solaris). So there is a real challenge here to try to
    > provide something at least as good and universal because we know that it can
    > exist. And this is what you finally did : work on a scheduler which ought to be
    > good with any workload.

    Solaris has a pluggable scheduler framework (each policy --
    OTHER/FIFO/RR/etc. -- is it's own separate component).

    Nicholas Miell <>

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