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    SubjectRe: Why preallocate pmd in x86 32-bit PAE?
    Linus Torvalds wrote:
    > So don't do it. Just preallocate for the magic 4-entry PGD. You can make
    > the special case just be something like
    >

    Yes, OK, it makes sense. Conceptually they would be dynamically
    allocated and freed, but they'd just happen to start allocated, to avoid
    the tlb flush of populating the pgd of an active pagetable. If you
    happened to do a 1G munmap, it may end up freeing and reallocating them,
    but that's going to be very rare. Either way, the other special cases
    are avoided (though pgd_populate would still need to be correct, on the
    offchance it gets invoked).

    J
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