Re: [PATCHv3, RFC 32/34] thp: handle write-protect exception tofile-backed huge pages

From: Kirill A. Shutemov
Date: Fri Apr 26 2013 - 11:29:13 EST

Dave Hansen wrote:
> > + if (!PageAnon(page)) {
> > + add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
> > + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
> > + }
> This seems like a bit of a hack. Shouldn't we have just been accounting
> to MM_FILEPAGES in the first place?

No, it's not.

It handles MAP_PRIVATE file mappings. The page was read first and
accounted to MM_FILEPAGES and then COW'ed by anon page here, so we have to
adjust counters. do_wp_page() has similar code.

Kirill A. Shutemov
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at