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    SubjectRe: subobj-rmap
    On Sun, 6 Apr 2003, Martin J. Bligh wrote:

    > Supposing we keep a list of areas (hung from the address_space) that
    > describes independant linear ranges of memory that have the same set
    > of vma's mapping them (call those subobjects). Each subobject has a
    > chain of vma's from it that are mapping that subobject.
    > address_space ---> subobject ---> subobject ---> subobject ---> subobject
    > | | | |
    > v v v v
    > vma vma vma vma
    > | | |
    > v v v
    > vma vma vma
    > | |
    > v v
    > vma vma

    OK, lets say we have a file of 1000 pages, or
    offsets 0 to 999, with the following mappings:

    VMA A: 0-999
    VMA B: 0-200
    VMA C: 150-400
    VMA D: 300-500
    VMA E: 300-500
    VMA F: 0-999

    How would you describe these with independant
    regions ?

    For VMAs D & E and A & F it's a no-brainer,
    but for Oracle shared memory you shouldn't
    assume that you have any similar mappings.

    I don't see how the data structure you describe
    would allow us to efficiently select the subset
    of VMAs for which:

    1) the start address is smaller than the address we want
    2) the end address is larger than the address we want

    Then again, that might just be my lack of imagination.



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