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    SubjectRe: Linux-2.5.16


    On Tue, 21 May 2002, Linus Torvalds wrote:
    >
    > For example, in the exit_mmap() case, we should tear down the page tables
    > in top-to-bottom order, and that makes all the "tlb->pages[]" stuff
    > entirely unnecessary: we can just remove the _top_ pgd, and once that is
    > done (and the TLB invalidated), we can remove the pmd's and the pte's at
    > our leisure without any fear of races.

    Hmm.. We could simplify it even further by moving the exit_mmap() from
    mmput() into mmdrop(), at which point we know that we exit the mm only
    after nobody is using the thing any more at all, and it has been flushed
    from the TLB's.

    The only downside of that is that we currently do the mmdrop in the middle
    of the context switch, and we'd have to move it to _after_ the context
    switch. Which is slightly complicated. The other problem is that with lazy
    TLB's, we might delay actually freeing the pages for a longish time
    especially on big SMP machines (if the MM ends up being lazy on an idle
    CPU for long)..

    So while this approach would be absolutely wonderful from a TLB behaviour
    approach, it might not be the best approach in some other ways. Ideas?

    Linus

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