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    SubjectRe: [PATCH] 2.6.0 batch scheduling, HT aware


    Con Kolivas wrote:

    >On Tue, 23 Dec 2003 12:36, Nick Piggin wrote:
    >
    >>Con Kolivas wrote:
    >>
    >>>I discussed this with Ingo and that's the sort of thing we thought of.
    >>>Perhaps a relative crossover of 10 dynamic priorities and an absolute
    >>>crossover of 5 static priorities before things got queued together. This
    >>>is really only required for the UP HT case.
    >>>
    >>Well I guess it would still be nice for "SMP HT" as well. Hopefully the
    >>code can be generic enough that it would just carry over nicely.
    >>
    >
    >I disagree. I can't think of a real world scenario where 2+ physical cpus
    >would benefit from this.
    >

    Well its the same problem. A nice -20 process can still lose 40-55% of its
    performance to a nice 19 process, a figure of 10% is probably too high and
    we'd really want it <= 5% like what happens with a single logical processor.

    >
    >>It does
    >>have complications though because the load balancer would have to be taught
    >>about it, and those architectures that do hardware priorities probably
    >>don't even want it.
    >>
    >
    >Probably the simple relative/absolute will have to suffice. However it still
    >doesn't help the fact that running something cpu bound concurrently at nice 0
    >with something interactive nice 0 is actually slower if you use a UP HT
    >processor in SMP mode instead of UP.
    >

    It will be based on dynamic priorities, possibly with some feedback from
    nice as well, but it probably still won't be perfect and it will probably
    be very complex *cough* hardware priorities *cough* ;)

    I might try to fit it into a more general priority balancing system because
    we currently have similar sorts of failings on regular SMP as well.


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