Re: [RFC] Page table sharing

[Linus Torvalds <torvalds@transmeta.com>]

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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