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    SubjectRe: [ckrm-tech] [RFC] [PATCH 0/3] Add group fairness to CFS
    On Thu, May 31, 2007 at 02:15:34AM -0700, William Lee Irwin III wrote:
    > Yes, the larger number of schedulable entities and hence slower
    > convergence to groupwise weightings is a disadvantage of the flattening.
    > A hybrid scheme seems reasonable enough.

    Cool! This puts me back on track to implement hierarchical scheduling in
    CFS :)

    Once this is done and once I can get containers running on a box, I will
    experiment with the flattening trick for user and process levels inside
    containers.

    Thanks for your feedback so far!

    > Ideally one would chop the
    > hierarchy in pieces so that n levels of hierarchy become k levels of n/k
    > weight-flattened hierarchies for this sort of attack to be most effective
    > (at least assuming similar branching factors at all levels of hierarchy
    > and sufficient depth to the hierarchy to make it meaningful) but this is
    > awkward to do. Peeling off the outermost container or whichever level is
    > deemed most important in terms of accuracy of aggregate enforcement as
    > a hierarchical scheduler is a practical compromise.
    >
    > Hybrid schemes will still incur the difficulties of hierarchical
    > scheduling, but they're by no means insurmountable. Sadly, only
    > complete flattening yields the simplifications that make task group
    > weighting enforcement orthogonal to load balancing and the like. The
    > scheme I described for global nice number behavior is also not readily
    > adaptable to hybrid schemes.

    --
    Regards,
    vatsa
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