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    SubjectRe: [PATCH] add b+tree library

    I only listed the proposals I've heard about before, not necessarily
    endorsing them.

    > The number of people that truly understand what Judy trees do may be
    > single-digit. Main disadvantage I see is that Judy trees heavily rely
    > on repacking nodes over and over. Part of Judy is a memory manager with
    > essentially slab caches for nodes with 2, 4, 6, 8, 12, 16, 24, 32, 48,
    > 64, 96, 128, 192, 256, 384 and 512 words.

    Well complicated code is en vogue recently :-)

    > Splay trees are still binary trees, so the fan-out argument is identical
    > to that against rbtrees. If we have to pull in a cacheline, we might as
    > well use all of it.
    > Skip lists are just a Bad Idea(tm). In O(x) notation they behave like
    > binary trees, waste cachelines left and right, use more memory, depend
    > on a sufficiently good random() function,... I guess you never closely
    > looked at them, because anyone who does tries to forget them as fast as
    > possible.

    Using the radix trees more would be also an alternative.

    I honestly don't know how they will all perform in the kernel that is why I
    thought it would be a good idea to just try them out. But I'm not
    volunteering to code it up, so it was more an idle thought.

    Doing that would be a reasonable student project. In fact I've been asked
    about this sort of thing by students in the past.

    Cleaning up the rbtree interface to be a little more abstract
    would be probably a good idea in general. I never really
    liked the open coded searches.


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