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    SubjectRe: [PATCH 2 of 4] Introduce i386 fibril scheduling

    * Mark Lord <lkml@rtr.ca> wrote:

    > >also, we context-switch kernel threads in 350 nsecs on current
    > >hardware and the -rt kernel is certainly happy with that and runs all
    > >hardirqs
    >
    > Ingo, how relevant is that "350 nsecs on current hardware" claim?
    >
    > I don't mean that in a bad way, but my own experience suggests that
    > most people doing real hard RT (or tight soft RT) are not doing it on
    > x86 architectures. But rather on lowly 1GHz (or less) ARM based
    > processors and the like.

    it's not relevant to those embedded boards, but it's relevant to the AIO
    discussion, which centers around performance.

    > For RT issues, those are the platforms I care more about, as those are
    > the ones that get embedded into real-time devices.

    yeah. Nevertheless if you want to use -rt on your desktop (under Fedora
    4/5/6) you can track an rpmized+distroized full kernel package quite
    easily, via 3 easy commands:

    cd /etc/yum.repos.d
    wget http://people.redhat.com/~mingo/realtime-preempt/rt.repo

    yum install kernel-rt.x86_64 # on x86_64
    yum install kernel-rt # on i686

    which is closely tracking latest upstream -git. (for example, the
    current kernel-rt-2.6.20-rc7.1.rt3.0109.i686.rpm is based on
    2.6.20-rc7-git1, so if you want to run a kernel rpm that has all of
    Linus' latest commits from yesterday, this might be for you.)

    it's rumored to be a quite smooth kernel ;-) So in this sense, because
    this also runs on all my testboxes by default, it matters on modern
    hardware too, at least to me. Today's commodity hardware is tomorrow's
    embedded hardware. If a kernel is good on today's colorful desktop
    hardware then it will be perfect for tomorrow's embedded hardware.

    Ingo
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