On Mon, 18 Jun 2012 15:11:42 +0300
Avi Kivity <avi@xxxxxxxxxx> wrote:
> Potential for improvement: don't do 512 iterations on same large page.
>
> Something like
>
> if ((gfn ^ prev_gfn) & mask(level))
> ret |= handler(...)
>
> with clever selection of the first prev_gfn so it always matches (~gfn
> maybe).
I thought up a better solution:
1. Separate rmap_pde from lpage_info->write_count and
make this a simple array. (I once tried this.)
2. Use gfn_to_index() and loop over rmap array:
...
/* intersection check */
start = max(start, memslot->userspace_addr);
end = min(end, memslot->userspace_addr +
(memslot->npages << PAGE_SHIFT));
if (start > end)
continue;
/* hva to gfn conversion */
gfn_start = hva_to_gfn_memslot(start);
gfn_end = hva_to_gfn_memslot(end);
/* main part */
for each level {
rmapp = __gfn_to_rmap(gfn_start, level, memslot);
for (idx = gfn_to_index(gfn_start, memslot->base_gfn, level);
idx < gfn_to_index(gfn_end, memslot->base_gfn, level); idx++) {
...
/* loop over rmap array */
ret |= handler(kvm, rmapp + idx, data);
}
}
Thanks,
Takuya
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