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    SubjectRe: [patch 1/2] ufd v1 - unsequential O(1) fdmap core
    On Mon, 4 Jun 2007 06:05:22 -0700 (PDT) Davide Libenzi <davidel@xmailserver.org> wrote:

    > On Mon, 4 Jun 2007, Andrew Morton wrote:
    >
    > > a) Were IDR trees evaluated and if so, why were they rejected?
    > >
    > > b) it's a bit disappointing that this new allocator is only usable for
    > > one specific application. We have a *lot* of places in the kernel which
    > > want allocators of this type. Many of them are open-coded and crappy.
    > > Some use IDR trees.
    > >
    > > If we're going to go and add a complete new allocator, it would be
    > > good to position it as a library thing if poss.
    >
    > Thank you for pointing me to that, Andrew. I didn't know about it (IDR
    > trees).
    > It does not fit AFAICS.
    > Locking should be handled extarnally (the files
    > struct),

    Yeah, that's already a problem in IDR and I'm hoping sometime someone will
    be inspired to redo it, move it to caller-provided locking.

    > must be RCU friendly (proper barriers) since it's used in
    > lockless code,

    Haven't looked at that.

    > and must have flags associated to an allocation.

    Don't understand that.

    > And I'm
    > leaving out the O(1) part, that for something like this, is just silly not
    > to have it. This is really an array.

    Having to walk down a tree in fget_light() would kinda suck.

    What about my b)?
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