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    SubjectRe: [RFC][PATCH 09/22] sched: add period support for -deadline tasks
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    On Thu, 2010-11-11 at 20:17 +0100, Peter Zijlstra wrote:
    > On Fri, 2010-10-29 at 08:34 +0200, Raistlin wrote:
    > > Make it possible to specify a period (different or equal than
    > > deadline) for -deadline tasks.
    > >
    > I would expect it to be:
    >
    > runtime <= deadline <= period
    >
    Well, apart from that really unhappy comment/changelog, it should be
    like that in the code, and if it's not, it is what I meant and I'll
    change to that as soon as I can! :-)

    Since you spotted it... The biggest issue here is admission control
    test. Right now this is done against task's bandwidth, i.e.,
    sum_i(runtime_i/period_i)<=threshold, but it is unfortunately wrong...
    Or at least very, very loose, to the point of being almost useless! :-(

    The more correct --in the sense that it at least yield a sufficient (not
    necessary!) condition-- thing to do would be
    sum_i(runtime_i/min{deadline_i,period_i})<=threshold.

    So, what you think we should do? Can I go for this latter option?

    Thanks,
    Dario

    --
    <<This happens because I choose it to happen!>> (Raistlin Majere)
    ----------------------------------------------------------------------
    Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa (Italy)

    http://blog.linux.it/raistlin / raistlin@ekiga.net /
    dario.faggioli@jabber.org
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