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    SubjectRe: elevator algorithm bug in ll_rw_blk.c
    > With that kind of knowledge, what kind of improvements could be made to
    > the driver?

    actually, it's the true geometry that a disk scheduler wants,
    along with a model for how long a given seek will take.
    hdparm gives neither: the geometry is false, because all non-ancient
    disks are zoned, and it doesn't mention seeking (which is a
    nonlinear function in any case), or head-switching time.

    fortunately, none of this matters much, since seeking is still basically
    monotonic with distance in _blocks_. this is why the current request
    sorting (even before the fix) can easily deliver maximal bandwidth.
    it basically only errs when you generate a new request at a lower
    absolute address (thus deferred by the sort), that in truth is in
    the current track, and would be very fast to fetch. that's a fairly
    obscure pattern...

    regards, mark hahn.

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