On Wed 26-09-18 00:00:02, Kirill A. Shutemov wrote: > On Tue, Sep 25, 2018 at 08:30:19PM +0200, Michal Hocko wrote: > > On Tue 25-09-18 14:51:53, Kirill A. Shutemov wrote: > > > On Tue, Sep 25, 2018 at 12:55:33PM +0530, Ashish Mhetre wrote: > > > > TRANSHUGE pages have no migration support. > > > > > > Transparent pages have migration support since v4.14. > > > > This is true but not for all architectures AFAICS. In fact git grep > > suggests that only x86 supports the migration. So unless I am missing > > something the patch has some merit. > > THP pages are movable from the beginning. Before 4.14, the cost of > migration was THP split. From my PoV __GFP_MOVABLE is justified and we > should keep it there. A very good point! I haven't really looked closer to what happens in the cma/migration code when the migration is not supported. As you've said THP migt be split into 4kB pages and those are migrateable by definition. So I take back my proposal and if this doesn't work properly now then it should really be handled by splitting up the thp. Thanks and sorry I've missed this! -- Michal Hocko SUSE Labs
