On Wed 30-06-21 12:22:48, Matthew Wilcox wrote:

On Wed, Jun 30, 2021 at 10:30:38AM +0200, Michal Hocko wrote:

quoted

quoted

-	if (PageAnon(page)) {
-		if (page_mapped(page)) {
+	if (folio_anon(folio)) {
+		if (folio_mapped(folio)) {
 			__mod_lruvec_state(from_vec, NR_ANON_MAPPED, -nr_pages);
 			__mod_lruvec_state(to_vec, NR_ANON_MAPPED, nr_pages);
-			if (PageTransHuge(page)) {
+			if (folio_multi(folio)) {

Shouldn't be folio_transhuge? The resulting code is the same but
folio_transhuge is more explicit and matches the THP aspect.

I genuinely don't know.  For the benefit of those reading along, the
important part of the context is:

                if (folio_mapped(folio)) {
                        __mod_lruvec_state(from_vec, NR_ANON_MAPPED, -nr_pages);
                        __mod_lruvec_state(to_vec, NR_ANON_MAPPED, nr_pages);
                        if (folio_multi(folio)) {
                                __mod_lruvec_state(from_vec, NR_ANON_THPS,
                                                   -nr_pages);
                                __mod_lruvec_state(to_vec, NR_ANON_THPS,
                                                   nr_pages);
                        }
                }

We need to decide what 'NR_ANON_THPS' means in a folio-based world where
we have folios of all orders.  Does it count only the number of pages
in folios >= HPAGE_PMD_SIZE?  Or does it count the number of pages in
folios > PAGE_SIZE?

At this stage we only have PMD based, right? I believe it would be
simpler to stick with that at the moment and change that to a more
generic way along with other places which need updating.

Wrt. counters they do count pages so in this case this shouldn't be a
problem. But we do have counters for pmd mappings and that might need
some care.
-- 
Michal Hocko
SUSE Labs