On Mon, Jul 17, 2023 at 04:49:19PM +0100, Ryan Roberts wrote:
> > We're still doing one atomic op per page on the folio's nr_pages_mapped
> > ... is it possible to batch this and use atomic_sub_return_relaxed()?
>
> Good spot, something like this:
>
> } else {
> for (; nr != 0; nr--, page++) {
> /* Is this the page's last map to be removed? */
> last = atomic_add_negative(-1, &page->_mapcount);
> if (last)
> nr_unmapped++;
> }
>
> /* Pages still mapped if folio mapped entirely */
> nr_mapped = atomic_sub_return_relaxed(nr_unmapped, mapped);
> if (nr_mapped >= COMPOUND_MAPPED)
> nr_unmapped = 0;
> }
I think that's right, but my eyes always go slightly crossed trying to
read the new mapcount scheme.
