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    SubjectRe: rbtree scores (was Re: [patch] deadline-ioscheduler rb-tree sort)
    Andrew Morton wrote:
    > Jens Axboe wrote:
    > >
    > > As expected, the stock version O(N) insertion scan really hurts. Even
    > > with 128 requests per list, rbtree version is far superior. Once bigger
    > > lists are used, there's just no comparison whatsoever.
    > >
    > Jens, the tree just makes sense.

    Just a few comments about data structures - not important.

    Technically I think that a priority queue, i.e. a heap (partially
    ordered tree) is sufficient for the request queue. I don't know the
    request queue code well enough to be sure, though.

    Both heaps and trees are O(N log N), the difference being that an
    rbtree does a bit more constant-time work to balance the tree while
    maintaining a stricter ordering.

    If it was worth it (I suspect not), you can make a data structure
    which has O(1) amortised insertion time for a number of common cases,
    such as runs of ascending block numbers. Seems a likely pattern for a

    Implementing the latter would likely be a lot of work for little gain

    -- Jamie
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