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    SubjectRe: [RFC] Page table sharing


    On Tue, 19 Feb 2002, Daniel Phillips wrote:
    > >
    > > At that point you might as well make the TLB shootdown global (ie you keep
    > > track of a mask of CPU's whose TLB's you want to kill, and any pmd that
    > > has count > 1 just makes that mask be "all CPU's").
    >
    > How do we know when to do the global tlb flush?

    See above.

    Basically, the algorithm is:

    invalidate_cpu_mask = 0;

    .. for each page swapped out ..

    pte = ptep_get_and_clear(ptep);
    save_pte_and_mm(pte_page(pte));
    mask = mm->cpu_vm_mask;
    if (page_count(pmd_page) > 1)
    mask = ~0UL;
    invalidate_cpu_mask |= mask;

    and then at the end you just do

    flush_tlb_cpus(invalidate_cpu_mask);
    for_each_page_saved() {
    free_page(page);
    }

    (yeah, yeah, add cache coherency etc).

    Linus


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