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    SubjectRe: ima: use of radix tree cache indexing == massive waste of memory?

    * H. Peter Anvin <> wrote:

    > On 10/18/2010 09:48 AM, Eric Paris wrote:
    > > 1) IMA uses radix trees which end up wasting 500 bytes per inode because the key
    > > is too sparse. I've got a patch which uses an rbtree instead I'm testing and
    > > will send along shortly. I found it funny working on the patch to see that
    > > Documentation/rbtree.txt says "This differs from radix trees (which are used to
    > > efficiently store sparse arrays and thus use long integer indexes to
    > > insert/access/delete nodes)" Which flys in the face of this report.
    > Radix trees can efficiently store data associated with sparse keys *as long as the
    > keys are clustered*. For random key distributions, they perform horribly.

    For random key distributions hash and rbtree data structures are pretty good

    But the (much) more fundamental question is to turn the non-trivial allocation
    overhead of this opt-in feature into truly opt-in overhead.



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