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    SubjectRe: 4MB pages and framebuffer access, x11perf results, 2.1.125

    On Wed, 28 Oct 1998, Linus Torvalds wrote:

    > On Thu, 29 Oct 1998, MOLNAR Ingo wrote:
    > >
    > > the 4m issue is i think conceptually a granularity thing. Theres nothing
    > > wrong with unmapping the middle 4M of a 12M framebuffer mapping, no matter
    > > how rare it would be.
    >
    > There _is_ something wrong with it - namely that the VM layer has to know
    > how. [...]

    theres one more reason why it's a granularity type of thing: the vma's
    virtual address has to be 4M aligned too. Basically mmap() picks a generic
    4M-size vma, and only the driver-specific function knows that this is
    'incorrect'. We could hack this around by dropping the vma and
    reallocating it, but this is not quite robust.

    -- mingo



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