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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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