On 10.01.21 13:40, Muchun Song wrote: > If the refcount is one when it is migrated, it means that the page > was freed from under us. So we are done and do not need to migrate. > > This optimization is consistent with the regular pages, just like > unmap_and_move() does. > > Signed-off-by: Muchun Song <[email protected]> > Reviewed-by: Mike Kravetz <[email protected]> > Acked-by: Yang Shi <[email protected]> > --- > mm/migrate.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 4385f2fb5d18..a6631c4eb6a6 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t > get_new_page, > return -ENOSYS; > } > > + if (page_count(hpage) == 1) { > + /* page was freed from under us. So we are done. */ > + putback_active_hugepage(hpage); > + return MIGRATEPAGE_SUCCESS; > + } > + > new_hpage = get_new_page(hpage, private); > if (!new_hpage) > return -ENOMEM; >
Question: What if called via alloc_contig_range() where we even want to "migrate" free pages, meaning, relocate it? -- Thanks, David / dhildenb
