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    SubjectRe: 2.6.4-mm1
    Andi Kleen wrote:

    >>>Some kind of SMT scheduler is definitely needed, we have a serious
    >>>regression compared to 2.4 here right now. I'm not sure this
    >>>is the right approach though, it seems to be far too complex.
    >>>

    Andi, I'll agree that the way domains currently get set up is pretty
    ugly. Maybe some additional functions or macros could be used to make
    this process a bit clearer.

    The actual kernel/sched.c code is really not that complex. In some ways
    it is *less* complicated than the old numa scheduler because it all goes
    through one code path.

    It also handles SMT, which is where a bit of complexity is coming from.
    The other alternative is shared runqueues which is uglier and less flexible.


    >>Well that's discouraging. I really do want to push this thing along a bit.
    >>
    >>Yours is the only report of regression of which I am aware. Is the reason
    >>understood?
    >>
    >
    >I think the reason is that it doesn't do balance on clone/fork. The
    >normal scheduler also doesn't do that, but for some reason it still does
    >better on the benchmarks (but worse than the old 2.4 -aa/Intel O(1) HT
    >scheduler)
    >
    >

    There have been a few changes and bug fixes since you last tested.
    Maybe that would help.

    >>And is anyone developing alternative SMT enhancements?
    >>
    >
    >I thought there was a patch from Ingo Molnar? ("shared runqueue")
    >I must admit I never tried it, just remember seeing the patches.
    >

    Yep shared runqueues. Ingo and Rusty both had implementations but
    they both agreed sched-domains was a better alternative.


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